Motor plate thought?

DrCharles said

I wouldn't use nutserts either! That rail sheet metal is pretty thin.
I used 3/8" Grade 8 bolts, a thick wall spacer as noted (just a hair below flush with both the top and bottom), a flat washer, lockwasher and nut underneath the rail. This is the view looking straight down before bolting the mount on.

View attachment 1715674828

Click to expand...

if doing this again drill the small (3/8) hole on top of the rail and feed the tube up from below. that way the top of the rail is sandwiched between the tube and the new mount so it can't 'shuffle' at all once assembled. basically the same as when fitting a towbar that bolts to a unibody chassis rail, the side of the chassis that the towbar bolts to is sandwiched in place.
neil.