I had 60-1 for about 2 years I think.
No issues, with it till it finally blew oil seals and started to burn oil/smoke.
Fun turbo to have.
Ran it on 20-25 psi the whole time I had it.
I have 550's with Walbro and other goodies, AFRs are rich with my PT6265, around 11.5 and all the way down to where my wideband maxes out. That's on 20 psi.
Base FP is ~43 psi.
I think you should be good to around 17-18 psi with proper tune.
I don't know if you have a wideband, but you should really get it, also get a exhaust temp sensor, that way when your wo2 dies, you can still monitor your temp.