I have an older set of Minoura rollers
4 (or 4.5) inch drums.
I rode the Cyclops rollers and there is a good
deal of difference (at least in my opinion).
Warped rollers? thats very unusual for aluminium,
tend to hear that about PVC rollers.
FWIW Xavier who runs a shop, recommended PVC for
the simple reason that if you drop something on Alu
rollers they dent.
Did you check out the Kreitler web site?
lots of good info there.

Marty