Good advice from all, thanks. My drysuit is also an O'neill. The bottoms come up over my shoulders, overall style, and afford a good bit of protection to my chest area even without the dry suit top. Since it is the top that causes the chafing I think I'll just use the overall part and substitute a decent, paddle jacket for the top. It should be way more comfortable anyway to paddle with a breathable top. The duct tape idea sounds intriguing, in a weird sort of way. I may try that for rolling practice with the drysuit top.
thanks again,
Mark