The back wheel on my SS keeps moving in the horizontal dropouts when I push extra hard on the pedals. The chain line is pretty damn straight when set up.

Anyone know if I can convert a Hope XC rear hub from Quick Release to a threaded axle? I couldn't find any such parts on the Hope website.

Or is there another way to stop the wheel moving?

I'm not sure, your best bet would be to ask the guys at hope themselves.. They're very helpful.

Last time I emailed Hope with a technical query, I didn't get a reply...

Just ring them, 01282 851200 IIRC

just tap the inside ends of the axel with relevent tap and use relevent bolts to secure into frame

done it many a time on dh bikes , pioneered on my old coyote back in 19oatcake when the wheel kept moving