[masraum]

Originally Posted by look 171

No sander. You will end up with valleys and hills and you will want to throw both sander and yourself out the window after a couple hours covered in dust.

good to know, thanks. Of course, once sanded, it'll never been seen again.

Someone made those cabinets, not bought from a bog box store.

Yes, 100% custom. I am not/was not impressed with the work that was done, but they are sturdy.

Lets split hair for a second. That side looks to be an imported plywood so its more then likely a little thinner then 3/4". You need 11/16, so that's only 1/16 you need to shave down. Technically that will work, but somehow, the gods ain't with people like us on such horrible product, plywood, so you are correct, 1/8 is what you need ( doesn't matter thickness of plywood at this point). I know you have a router, but if you really want to abuse yourself, make a carriage along with a 3/4" straight cutting bit and set the router to cut 1/8 off after 1000 passes to achieve the 1/8" off the side of the cabinet. Its actually more accurate then the power plane. Me, I buy the plane and have everything in place, be done before dinner.

Yes, the plywood is 11/16", and yes, it's cabinet plywood, but probably the cheapest available.
I do have an old router, but don't want to go that route (no pun intended). I'd rather take my chances with the belt sander than use the router. One the cabinet is thinner, the side that I alter will never be seen again because it'll be screwed up against the cabinet next to it. I'll look into the planer. Wouldn't the planer be more likely to chew up the cheap ply?