I noticed that you size your carcass plywood at 3/4″ and the stile that would be attached in front of two adjacent box sides at 1-1/2″. Plywood is actually 23/32″. Do you place a spacer between adjacent boxes to make them 1-1/2″ to match the stile? If not, they won’t be even with the stiles edges, and drawer slides won’t be straight. Just curious.
Actually, plywood thickness is not the same from batch to batch. It can be 3/4″, it can be 23/32″ or anywhere in between. And you can buy plywood that is 3/4″ at a premium price. But to answer your question, Greg does put a spacer between his sides.
Historically, I’ve just used veneer that I have lying around as shims. However, lately, I’ve been leaning more towards plastic shims I’m getting from http://www.handi-shim.com/
They come in handy all over the shop and there’s little holes in them that fit nicely over the barrel bolts that hold the cabinets together and you’re done. The smallest one they make is 1/32″ which is typically just about right. If I can’t use those, I drop back to veneer.