thinking of welding a threaded tube into the rear stays of the roll bar for rear mounts,would it be ok for 4 points to be fixed this way,ie both rear straps on 1 mounting point with the bolts coming towards wach other?

the SVA manual shows examples of mountings; check that yours is one ofthe accpetbale ones.

my idea isnt shown,maybe ill do it the normal way then

"seat belt mountains"

Thats a large pile of seat belts!

(Sorry, couldn't resist)

wos rong wiv me speelin?

Im not quite sure what you mean by your description (do you mean using 2 threaded tubes welded horizontally, one for each side rather than the normal 4 welded vertically - both seat belt bolts screwing into the same threaded bar)??

I know if you use the roll bar to fix seat belts to you have to pay attention to how the roll bar is fastened to the chassis. Can you not just weld 4 threaded tubes to the back of the chassis? This depends on chassis height and what angle the belts will go from chassis thro slots in seat of course.