Hello from Lancs

[irving2008]

I'd be surprised if you got that much a temp difference between screw and bed rail given they're only going to be a couple of 100mm apart or so.I'd turn the screw end down to say 15 or 12mm depending on root depth and put a similar clearance hole through the end box section with an anti-crush tube inside and thread the last 20mm of the screw for the tensioning nut and thrust washer. You could look at back to back Bellevue washers to get a defined preload.