When I first converted my Wicked Fat to singlespeed I used a random shimano middle ring- pinned, ramped, etc and an 8 spd chain. The chain fell off all the time. slight uphills w little pressure on the pedals, downhills at moderate rpms. totally unreliable when going any faster than a leisurely pace. A cheapo 6061 unramped and pinned chainring was put on. zero chain derailment issues. Maybe it was just me, but I think think the chain was catching the shifting ramps at just the right time and specially shaped teeth just dumped the chain right off.