Yea, but most MTB use horizontal dropouts, so most of that force is on the actualy dropout, not the QR. The QR really just needs to be tight enough to the wheel doesn't fall out. Of course disc brakes cause a whoe mess of issues.

You mean vertical dropouts, right?

He may have indeed, but before they used vertical they used horizontal and didn't have any issues. THe lower the gear, the more pull there is on the chain. There are thousands of bikes with QR hubs, horizontal dropouts and lower gear ratios than FG and they don't have issues when fastened correctly.

In Rand McNally, hamburgers eat people.

My rear wheel kept slipping on my ss with QR. I just installed a solid axle this week. Guess what - it slipped too. Now I've got it cranked down (bigger hammer, and all that), so I hope this is over.

put some grease (if you haven't already) on the axle so you can tighten the nuts more or maybe your chainring isn't centered on the crank and you're chain is too tight?

Thx for the suggestions. I forgot about centering the crank. I read about it when I did the original conversion, but forgot to do it. It makes sense that the chain tension might look OK where I happen to check it, but be too tight in another part of the rotation.

Didn't know about the grease. I'll try that also.