Bongo Fury

The way I did it was to fit the long rail with the existing fixing points (not tight) and use a pin punch to mark the approximate centre of the new fixing points such that it dented the metal (its pretty thin). Remove the rails. This showed up the rough/faint outline of the hole.
I then used a centre punch to spot nearer the centre if I was a bit out.
Then I used a hole saw with a small pilot drill so I didn't damage the thread and the hole saw size was 20 - 25mm. The hole saw removed the thin sheet metal which wasn't attached to the frame underneath without going anywhere near the thread.

Regards Grahame

yeeeha

job done at campers scotland. I can now put me seats where ever I want.

I kind of broke the kitchen unit on the way home as it was detached form the van and fell over but I think it was a bit of a "homer" job in the first place.

Gary at campers scotland seems very nice and helpful. With a bit of luck he will open another place in Aberdeenshire somewhere!