My old man has one (not a Golight but similar) but not a great light, although it is controllable. Just very handy for lamping on your own. Ideally the Golight would be a much better quality lamp beam-wise.
I've always swithered about just cutting the hole in the roof, I'm not bothered about the truck,I'll have her until she id beyond repair, but I swear the wife would forget the lamp was there and clatter it in a multi-storey.
I'll get a look at your Cluson jobby in a couple of weeks Paul, does Mike Davies sell them ?