6 plus 6 is 12. Have you attempted a shift to get a 12 in cab..just one? Or a nine inch cabinet on one side and 3 in filler before the corner setup? I think I would NOT be interested in a plan with 6 inches left over both left and right of sink. The particular layout, if you show it, may easily be adjusted to improve this.

I hear you, Herbflavor - and appreciate the thought. The challenge is I'd like my sink to be centered under the window so the space just isn't flexible. My other option seems to be just going with a bigger sink base (what I currently have) and filler panels. Was just trying to get a little more usable space in a challenging layout.

many undermount sinks can have the FAUCET centered at a window-or close to being centered.....[and the faucet is much more visible]...so the sink itself can be shifted....there is no rim, so the position to the eye is not critical.

I'd go for a bigger sink cabinet, even if you don't get a bigger sink. That's a whole foot of kinda usable space, with the proper after market organizers. The 6" pullout won't offer much.

The OP is talking about filler pullouts, not cabinets. Filler pullouts have no walls so the majority of the space is used. The pullout is attached to the walls of the adjacent cabinets.

I'm not a kitchen designer, but if you want to stick with your current sink cabinet size, there are many cabinet companies that make 6-inch spice, wine, and/or storage cabinets. While they might not be the trendiest cabinets, they can be very handy and look good! Since one would be going beside the dishwasher, you would need to watch what you put there with all that heat. I did a quick search for Medallion cabinets specs and this catalog came up right away--just as an example. http://www.medallionatmenards.com/wcsstore/lkcontent/marketing/medallion_at_menards/menards_planning_guide_1-15.pdf

Yes - you can do a 6" filler with Revashelf behind it. Here's a 3" in our showroom, also available in 6". Spice racks come in the same sizes. And as mentioned above, this would be built as an attachment to the adjacent cabinets - not a separate cabinet. Your installer should be able to create a toe kick and such for the bottom.

Transitional Display in Edmond Showroom · More Info

Filler pull outs are required to be placed between cabinets. Or, you need a 3/4” panel. The math needed to make 6”’of space work usually means that you are down to a 3” filler pull out by the time the panels etc are done. For a LOT of money. As much as a 36” cabinet.

By the time you get through trying to not “lose” storage space in stock cabinets, you could move up a grade to a line that allows more customization for their products. I’ve done semi custom 6” tray bases frequently when the space between the sink and corner wouldn’t allow for anything else.

Like others have mentioned, I am curious why you aren't getting a wider sink base cabinet instead. Can you please explain? Also, how large is your sink with the current plan?

Vertical drawers just deep enough (<6" ) and designed/created specifically for spices on your left and a "wall" for hanging cooking utensils -- large spoons, spatulas, etc. -- on your right (if you're right handed) would be worth considering.

https://www.google.com/search?q=base+cabinet+kitchen+vertical+drawers&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjY3ueX8qzeAhUSmuAKHZ0VASEQ_AUIDygC&biw=1366&bih=650