I bought my harnesses second hand, so dont have instructions... or SVA, so..
- I have flat bar type mounts, rather than the clip type, and Ive welded in 3mm plate where appropraite.
So, do I have to have captive type mountings on the bottom mounts, eg welded on nuts, or can I use a normal high tensile 10 mm bolt, washers and lock nuts?
I intend to mount the top mounts on the roll bar horizontal

you need 7/16 unf bolts and nuts welded to the mounting points

Captive nuts may make it more convenient, but i doubt if it would be a SVA requirement.
You could always remove the special seat belt bolts (thin domed heads) and crush tubes from a wreckers. That way, your belts will swivel in the direction of tension. That doesn't always happen with fixed bolted belts.....until an accident. All of a sudden, they can align with the direction of tension, sometimes lengthening the belt in the process!

Someone on here checked with their local SVA place - captive bolts aren't a requirement, but they are convenient.

What is a requirement is a solid mounting point - they will be looking for strong mountings on structural chassis members (there are diagrams in the SVA manual). This means spreader plates, thick backing plates, or similar, fixed into the spaceframe with plenty of good welding.

cheers,

David

I ran a 12mm drill through the crush tubes, it only takes a fine shave off them, and then used M12 bolts with nyloc nuts as unless you take part of the old car inner sill the 7/16 unf nut goes with it.

yours, Pete.

Surely you'd want 'Never crush' tubes?

It's a circular tube with shoulder on it so the metal ends of the belt can swivel round and get lots of twists in them .

yours, Pete.