RealNice!
Not affraid of a challenge are you!
That Cane speaker grill is a bear to work, and getting it as flat and straight as you did is amazing, ESPECIALLY for a first time.
So if that wasn't enough of a challenge, you threw in some piping too!
I'd built about half dozen cabs or more before I tried my hand at piping!
It is
VERY obvious you took a lot of time on this project and moved slowly and carefully.
I would have liked to seen the cab construction. Dove tailed joinery is beautiful. a shame to cover it.
As far as the corners go, they are a bit difficult. I've got maybe 20 cabs now under my belt and have yet to make 8 perfect corners in a row. Like you've said, those corners can hide a ton of ugly

On a couple I've used vinyl floor adhesive from Lowes,which is the same thing I found out later as the water based contact adhesive (ammonia like smell) .
It was my least favorable to work with, but I will say I found it to be tenacious.
The last cab I built I used hot hide glue. I'm in love now with it and think it may be THE way to go. The heat from the glue softens the vinyl nicely and lets me conform it to inside curves and compound radii very nicely. The drawbacks is you to work in sections, quickly, REAL quick! and don't miss a bubble or a glob under the tolex!
One of these days, I'll have joinery as nice as Tubenits and be able to do what he does, he showcases his construction and foregoes the tolex. They end up looking very much like fine furniture.
Great Job!
I just need to do the hard part and wire everything inside the chassis.
Judging from your mechanical skills this part should be a breeze for you!
Post pics as you go!