Newbie new build

[Clive S]

Also to reduce materials; at a cursory glance if you wanted side mount rails I wonder if you would gain strength and reduce flexing movements by putting those rails on the inside of the frame?
(Though no doubt you'd probably lose some working width).

If you go the steel route mount the rails on the top as it is much easier, the way the epoxy works is that you make a moat on the two rails with a bridge between them this way the epoxy will flow around and give you the flat plane you require.

You use the very slow curing epoxy made by Wests 205 - 109 fluid for about 8 hours.

Search of the forum for epoxy levelling