I agree with the comment about MFSK16 being the optimal way to go. What I can't understand is the reluctance of folks to try it, or the idea that it is "hard to tune."
Bottom line, it isn't hard to tune at all. Line up on the "carrier" signal and there you are. Total piece of cake, even with weak signals (for the record, using MMVARI here). Had the same experience a while back on a PSK sked. The band just wasn't cooperating, and it would have been a wipeout had we not switched to MFSK. As it was, we continued with solid copy for another half hour. 73, Bill, K7JBQ