That does look nice. Lucked out finding that piece in the scrap.
Who knows maybe the raised edge will make it more rigid and help keep it straight.
Kinda surprised you didn't machine spots for small magnets into the bed,... something I saw on BIB's utube channel.
In this one, at 30 minutes, he discusses why he chose a mandela bed with the built-in magnets.
BIBs voron build isn't a 350. I think it's a 250mm.
I'm just starting to get this stuff figured out before I decide what kit to buy, behind you a few steps.
Build threads like this are really helping me understand what is required.