Well, this forum is for sharing successes, mistakes and failures.
In this case, I made a rookie mistake. I had my original jets separated in their own bag. When I put my new jets in, I assembled the carb sans main-jet washer.
The bike is all back together, and running great. Go figure. I'm definitely going to put the washer back on. I'm hoping I can do it without removing the carb this time.
Out of curiosity, what's the worst that could happen if someone forgot and never realized it? Would it simply affect performance?
Anyway, to all you noob carb tweakers to come, don't forget the main jet washer!!!!!

( Btw, I'm reeeally glad now I replaced the bowl screws with allen head stainless bolts and lock washers. Will make it 100x easier to get off without removing the whole carb. )