Thanks very much for the feedback. I'm familiar with biasing and indeed have experimented with different settings and found one that works for me (usually ends up being 60% or so of max dissipation).
But I guess I'm still confused if it's the PPIMV's circuit that doesn't allow the amp to "have the range to allow that much current with that set of tubes". Or, in my case, is it just that i have a low plate voltage amp? (i measured about 400v-405v)