It does sound like they'd be a bit "in your face". You might try using some painter's tape to hang a 4" deep box in front of some of your existing uppers and work on the counter with the box there to see how it feels. What kind of doors will you have? Doors will add depth beyond the depth of the box itself; a raised panel door will add an inch or so.

Also, anything near the back of the upper shelves would really be buried; you'd want pullouts/rollouts for those I think.

Since you're going custom... have you also considered raising your counters? I'm also tall as is DH and our 39" counters are much more comfortable than the old 36". In addition, the taller base cabinets gave us more storage space below the counter.

The cabinet I have over my cooktop is a 15" deep cabinet and the hood was made for 12". It was an easy fix. I had a metal fab shop make me a 3" strip with a lip on it to fill in the gap. I screwed the lip to the back of the hood making my 12" deep hood now 15" deep. It worked great.

Your countertops may actually be deeper than 24"-depending on if you do inset cabinets or note. I have frameless cabinets, with the doors the bases are 24 3/4". Then add on knobs/pulls. My granite overhands my knobs/pulls by almost an inch, so your countertop may be more like 26" deep or more.
OTOH I am tall as well and have hit my head on my sink cabinet so I would not go with deeper uppers.

Oh....I wanted to add something else too. I am tall, over 6'. I made darn sure I mounted my hood high enough that I would not bump my head on the corners. It's just high enough. The distance from the cooking surface to the hood is a few inches higher than the mfg suggests, but I have had no issues with the distance. It exausts just like it's supposed to.

We have a mix of 12" and 15" deep uppers and I wish they all could have been 15"! (Staggered depths work best with staggered heights + crown molding.) We have no problems working at the counter w/the deeper upper cabinets. We're also a tall family (5'10" to 6'6") and my children and I have very long arms (36/37 sleeve length for DD & me, 38" for DS!)

I would suggest no more than 15" deep for the uppers, though, b/c I think anything deeper will start to get in the way...and ChicagoAns is right, the doors will add another inch or so to the overall upper cabinet depth.

"Normal" counters are 25.5" deep. The standard base cabinet box is 24" deep, doors & drawer fronts are approx 1" thick/deep, and then you have your drawer pulls/knobs. Since the counter overhang should at least cover the the cabinet box and doors/drawer fronts (to prevent spills & crumbs from falling into the drawers or cabinets), the overhang should be at least 1" for a 25" deep counter. Additionally, it's a good idea to actually extend past the doors/drawer fronts a bit to direct spills away from the front of the doors/drawer fronts and, if possible, cover as much of the drawer pulls/knobs as you can...so that extra 1/2" is added for a total overhang of 1.5"....24" + 1.5" = 25.5"

You can make your counters a bit deeper either by deeper base cabinets (or base cabs pulled out from the fall) or by making the counter overhang deeper. 26" would be very reasonable, IMHO, if you just increased the overhang. If you have the space, though, I would increase the depth of your counters to at least 27", preferably 30"....and it isn't b/c of the deeper uppers, it's b/c deeper counters offer a lot more work space...more than you realize! If you can also get deeper base cabinets, then you add more storage as well. However, deeper base cabs are often prohibitively expensive for most of us so you could must pull your base cabinets forward 2" to 4.5" to get 27" to 30" deep counters.

I have 15" uppers on either side of my cooktop and they have both advantages and disadvantages. The storage for larger everyday items and my spices and oils is a big bonus. On the other hand I find it hard to tip out a large pot into a bowl or cassarole dish for serving unless I remember to move a little further down the counter or do it on the island. It isn't a big thing, but the first time I hit the cabinet with a pot I was a little shocked.

Not that it matters, but I am only 5'2". Good luck.

Perhaps upper cabinets should be shallower at the bottom (14'') and deeper at the middle (16'') and top (18''). That would maximize storage - you could fit platters, etc, on the topmost shelf - while minimizing encroachment. Figuring out the door swing would be interesting.

Hi. Just a different thought. I personally wouldn't do it because of the shadows under the cabinets. My plan has very few uppers with counter underneath, because the space underneath just feels like a dark hole to me, even when lit. Maybe because of my short arms. So I have open counters on one side, then floor to ceiling pantry style cabs.

On our stove wall we have 16" uppers because we wanted to hide a small microwave inside one of them. Our hood was also made for the standard 12" uppers, but it fit just fine. The only mistake we made was not allowing for the extra 4" when locating the recessed cans. They are a bit too close to the crown moulding, and we should have moved them out an inch or two.

We have no shadows, and do not even notice the difference between the wall with the 12" uppers and the wall with the 16" uppers. In fact, when we were first looking at cabinets, we found that for several European cabinet lines, 16" uppers were standard.

I would not do it. I have 13" deep uppers and when I use my big food processer and stand mixer I have to be careful not to hit the uppers when taking the stuff apart. You don't want to have to work close to the edge of the counter. My suggestion is to stay with the standard.

If the uppers are deeper, can they also be a bit shorter? Say, 2 inches?