I would say 15w50 oil is way too thick for a CVH. I've always run them on 10w40 semi synthetic and change it regularly. 10w40 fully synthetic is even better, but a lot dearer. The oil pressure you quote doesn't sound horrendous, i'm not sure what mine is as i've no pressure gauge. Just looked in Haynes manual, they say minimum oil pressure at 750rpm engine hot is 14.5psi, and 40psi at 2000rpm when hot. Get the right oil in it first, I would mate.