[Amps] YC156 operating parms for US amp build?

[Jim Barber]

Assuming all this YC156 chatter motivated me enough to start yet another 
project, I'm curious what a good set of operating parameters would be 
for a YC156 GG US-legal-with-significant-headroom amp?

My built-in seatofthepantsometer comes up with 5KV on the anode and a 
20-35V bias supply. I notice, though that others who have published 
YC156 projects on the web are running as much as 7KV on the anode, which 
at least appears to my untrained eye and the data sheet as being outside 
spec for the tube. ?

Also -
Harbach shows a 15V, 15A low-profile transformer in the amateur catalog. 
Since that happens to be exactly the YC156 filament requirement, would 
that be adequate? (I've always had that question about filament 
transformers in general, but haven't asked it out loud before)

So many questions...

Thanks,
Jim N7CXI