Hello, I've got 2 lass 66 loco's, 66 135 & 66 068, bought off of eBay. All my points are Peco mediums code 100 old stock, electrofrog, switched. Plus a couple of double slips SL-90. 66 135 copes with everything ok, but 66 068 has trouble with a curved left hand on the tighter radius side. It's the only point to cause trouble, the front bogie rides up the frog and drops off the rails. I've a feeling on the old RMweb someone had a problem with the same point and added a strip of plasticard to the check rail. Of course it could be something else, back to backs, etc. But it's the only loco to do it. Other than that the 66's are good performers.
HTH
Rob