Have you seen a picture of it yet? It might be that the 4x4 was to large for the space you wanted it in. Problem with building long distance is your control is minimal if you don't have it documented in both pictures and text.
But, back to your question....
no one here can tell you what to do. If this is a major thing for you and will effect the pleasure you'll have looking out that window while soaking, then make him take it out. If however, it's just an irritant then pick your battles! You've come a long way but, you've got a long way to go too.

Do you have it in writing? On the plans? Then there is no reason to accept the smaller window. It is a mistake, his mistake. This is not a HUGE deal to change out one window. Ask to see photos of the window -- interior and exterior. (Do you know all the other windows are correct?)

Do you have the specs for the size you wanted in writing? If not, it may become a case of 'he said, she said'.

It would seem relatively easy to enlarge the rough opening to accomodate a larger window - if - there is:
(a) room for the framing (including possibly a deeper header) needed to accomodate the larger window
(b) the siding can be cut to fit without having to tear it all off in that area.

Is that window close enough to the rim of the tub that you'll be able to see out when you are actually in the tub? Most folks put their windows too high to be of any use from the tub itself.

Remember too, windows are a two-way proposition. Will you have the privacy you want with a larger window?

Windows also are not all that thermally dense. A large window can make the tub area feel cold.

Finally, nearly ANYTHING can be fixed/changed. It just becomes a question of time and money.

I would want to see the window before I made the decision. Will you be visiting the site before insulation goes in?

If you aren't doing it already, I would back up all these conversations with a fax or email. It will help prevent errors and will provide back-up if this happens again.

I know for a fact that the window could and should be longer--not COMPLETELY SURE if the wall would accomodate a wider window like someone pointed out. BUT, I would've assumed if it was an issue with fitting the size we wanted, we would've heard from him that it wouldn't work and we needed a smaller window.

I honestly believe that he purposely chose to go a little smaller and shorter because he thought we were crazy for wanting a window so close to/over the tub. We went round and round on this--and thought we had the last word when we told him it's our house and this is what we want.

I was glancing through pics of the build...and it occured to me how small a 4X4 window looks from a distance/angle. I showed it to hubby, who said, "Hmmmmmm" and called his dad to go out to the house and measure.

The interior of the house is not going to be started until after we get up there to see everything in person so I think we would like to bring this to his attention in person to see what he says.

The answer depends on a lot of things, such as...
- What does your plan, as approved by your county, show?
- If it shows your larger windows, why does the builder say he changed it? Unless he's got a reason that convinces you it's the way to go, I'd insist on the larger windows.
- On the other hand, if your approved plan shows the smaller windows, it may not be possible to have the larger ones without having your plan re-engineered. It depends on the complexity of your plan, where your shear walls are, etc.
- Finally, how important are those windows to you? If this is your "forever" home and you really want those windows, I'd pursue getting them. We had several windows changed at your building stage (although in our case, most got smaller because we raised the sill height, which obviously didn't present a structural issue).

We're building our "forever" home, so have made several changes along the way that probably weren't very cost-effective. However, we knew we'd be living with whatever it was forever, so we just wanted it right (for us). DH often reminds me that almost any changes are possible. After all, people do drastic remodels all the time! :-)

Something to keep in mind - - a good builder has a lot of experience, so give his/her recommendations serious consideration. On more than one occasion, we thought we knew what we wanted, but when we actually went to the building site and the builder showed us the impact of the different choices, we ended up preferring his recommendation over what we thought we wanted. Keep an open mind, but remember, you're in charge (mostly). After all, it is your money.

I say if you asked for a specific size window it should have been purchased. If the window would not fit then you should have been informed and then you could decide what you wanted to do.
I have had several issues with this type of situation. My most recent was yesterday. We specifically stated several times our stair railing and spindels would be oak. We did not want white spindles. What do you think was in a box on the floor? White spindles. Those are going back to where they came from. Here we go again.
A few months ago I asked for my door in the kitchen to have the panes inside the glass as my windows. I chose exactly the door I wanted from the catalog. I was confident this selection would go smoother than the a few in the past. Wrong! The glass in the door is etched to look like panes. Pretty, however not even close to what I asked him to order. When I questioned him he even stated the exact door # from the catalog. I am still not sure why he put in this one. I guess he liked the one he installed better or it was in stock and he did not want to wait. The door is still there because I decided I could live with it just not to make waves.
My patients are wearing thin.
Do not settle for what is installed if you can not live with it.

Hee-hee, dragonfly! If you are a weight-loss doc, good on you -- otherwise, I'd be worried. LOL LOL (You couldn't have made your stress any more obvious than by writing that your "patients are wearing thin".)

We're going with a 4' x 4' window over each side of a corner tub. It might not sound like a foot is that much of a difference, but you're talking about a 78% increase in viewing area. That's a huge difference. I say seriosly consider it.