Raw built and fitted my roll-cage to my requests (far too unsophisticated to be called specifications).
It differs from Andy's in three respects:
1. I had the "standard height" roll-over bar behind the head replaced with a taller one (I think safer, and helps with scrute*)
2. my forward-and-aft bars are bent outwards to give a little more lateral protection
3. the forward loop is welded directly to the gusseted chassis immediately behind where the windscreen would be (I thought better strength and torsional stiffness).
Neither 1 nor 3 might be easy for a DIY fit.


HTH
Edited to say: * scrute might moan about a roll-cage which is a little lower than the regs demand, but he/she is very unlikely to try to exclude you because (unless this year's blue book has changed the regs) you could become legal with a road going car simply by removing the cage completely!!!
