Correct me if I am wrong, can the upper harness mounts be slipped over a horizontal roll cage tube, and fitted into their buckle ?
Or to be iva compliant do they require a welded threaded boss ?
If so are these harness clips likely to raise any eyebrows ?
http://www.racequipuk.com/racequip-race-harnesses-and-accessories/17-racequip-3-harness-snap-clip.html
thanks
What to look for:

Evidence that anchorages in a vehicle of the same or a very similar type have been subjected to a seatbelt anchorage strength test to “European
Standards” by a recognised authority. This may be acceptable where there is clear evidence that the structure is identical to the vehicle originally
tested.

Welding should appear neat and of good quality; whilst it is impossible to judge the quality of a weld just by looking at it, messy welding is rarely
strong welding.

Bolts used in structural areas should be of grade 8.8 or better. Such bolts will be marked 8.8 or 12.9 on the hexagonal head, however, cap-head bolts
or 7/16" ( 11mm ) UNF seat belt anchorage bolts (with an anodised finish) not marked in this way may normally be considered to be of equivalent
strength. Bolts should be M8 or larger.

Threaded bushes should be welded (at both ends) through the tube, and not end mounted on the surface. (A threaded bush may be attached by its side
surface to a structural component).
so does that mean you have to use threaded bushes? or just that if you do, then they have to be fitted like this?
since it comes last in the list, does that mean you can weld loops to the roll bar and use clip on belts? with no threaded bush etc? itsw open to
interpretation really. will probably turn out to not be the same as the testers though...
as for looping backthrough the clip, i think this bit might be important:
Evidence that anchorages in a vehicle of the same or a very similar type have been subjected to a seatbelt anchorage strength test to “European
Standards” by a recognised authority. This may be acceptable where there is clear evidence that the structure is identical to the vehicle originally
tested.
never seen a production one done like that, however, if the belt is FIA approved to be used like that, then it should be fine as FIA approval is good
for IVA.
hard to judge imo
I had read those sections and ended up as you have. It doesn't say you cannot loop belts on a horizontal tube, but then if I weld bosses in, they
won't be tested.
About as clear as mud.
Fairly happy I will do it the wrong way, with nothing forthcoming it's getting welded bosses.
Cheers Blake.