[tubman]

If the top three rings fit and have a proper modern oil ring, you can safely leave off the bottom ring set as they are redundant. The fourth ring was a "band-aid" used because of the inferior quality of the old style oil rings. When I built my last engine, I did a bunch of research and conducted discussions with guys on here and on the H.A.M.B. about this and came to the conclusion that the bottom ring can be left out because all it does is add extra drag to piston. I left them off, had the assembly balanced, and have not experienced any problems. I believe that I am not the only one who has done this in the past. I would just make sure I knew exactly what I was dealing with regarding proper fit and balance.