I finally got around to reading the fall edition of ProShop Operator, and there is an article by Dennis Bergendorf about unusual layouts that included the following on use of the full roller layout for lower 3/4 track players.
"This is for bowlers who want to tame, not enhance, ball movement. The pin being left of the thumb (possibly in the track) stabilizes flare in balls with higher diff. Liz Johnson has had success with the full roller. The pin being as far as 7 1/2" from the PAP may be even more dynamic than the more common placement of near the big finger hole.
"Higher track bowlers may find this layout causes the ball to roll over the thumb hole."
-- JohnP