First task was to cover the area with masking tape, offer up the roll bar and mark round the bottom. I tried to mark out the area of the bracket under neath as well as the couple of hole. This was hopefully to make sure the mounting bolts went through a solid area:
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I next drilled a pilot hole all the way through, removed the boot box and cut through the fibreglass using that largest hole cutter I had. I then widened out the hole using the Dremel:
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The body shell isn't quite symmetrical so the holes weren't quite in the same places on each side:
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I then followed a similar process to make the holes in the boot box. I first removed the majority of the material using a hole cutter. Offered up the roll bar and slowly made the holes bigger using the Dremel. It took me ages to do as I didn't want to remove too much and leave a gap:
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In the end I was really pleased with the fit: