Hadn't considered IVA man Johno. The Dome headed bolts have normal nuts, they're for atatching the roll-bar to Cp3/4. Hoping the rounded edges will get arung the projections/radius issues without needing plastic caps.
Here's a pic:
Its around 30mm long and threaded along the entire length. Will this keep Mr IVA happy? Do they need to be grade 8.8 on the roll bar or will standard be OK?