Today I put on my old Shimano 13-19 straight block, and it skipped under load. This is the end of my search, I put the original megadrive freewheel back on for the HHH in 3 days.

I don't recall problems with any of these freewheels when used on my road bike, with new or old chains. I don't know what's different about the Trek but I don't have time to fool with it any further, just ride it.