i would say the rings are wrong. sounds like they don't have enough tension against the walls causing them to spin. And...... if the rings are wrong what about the pistons? Has your mechanic actually pulled any pistons out? Do you have access to the part numbers of the rings and pistons used?
1981 Jeep CJ7 4.0 HO, AX-15, D300, D30, D44, SOA
1977 Chevrolet C/10 step side 454 TH400 3.73 posi