I hav had to cut some square holes trough my fibreglass tub to mount the rollbar to the chassis, Does anyone know of some trim that i can put round the the rollbar the seal the hole?

sikaflex or silicome?

or rubber u trim round the hole

Maybe have a look at some motocross sites - a common addition to most bikes is a neoprene seal around the forks to keep the muck out.

Try kriega - I know they do the seals, but I'm not sure of the sizes and whether it'll fit a roll bar

Maybe some 40mm waste pipe covers from the plumbing section of B&Q sprayed up to match the car colour?
Steve

Cut oversized rubber grommet (do they do them that big)

Have a try of a Witches Hat Cable Grommet Boat Steering Marine Cables on eBay (end time 13-Dec-10 08:32:04 GMT). I use them in work when I fit outboard engines to boats. You can get them in a few different sizes. Use the type with the ring like in the link so you can screw them down, there are a type that just pops into the hole but I don't like them and they probably wouldn't suit a square hole.

Gareth