RE: P-60 compressor
Hello,
I am not sure how Wren does it, but P-60s are balanced as a matched shaft assembly (Turbine wheel, shaft, compressor), then the compressor is removed and the the turbine reassembled with the compressor indexed as closely as possible to the balanced position. The turbine is then balanced AGAIN as a complete assembly in a special fixture.
So I don't know how it could be done at home skipping those 2 balance steps. But I will still ask Bob for you.
Regards,