Thanks for all the help everyone, I'm going to make the coast to coast on the inside like banditpowdercoat, because although it would be less obtrusive on the outside, to do that I would have to take a long thin section out of the back panel which is somewhat outside my comfort zone at the moment!
I notice that the Herbie style drain seems to be popular, I think I'll do something like that with a third emergency emergency drain because I'm paranoid (and the turbo snails seem to take delight in ending up in the weirdest/most impossible places). I figure that if I use 1.5" tube instead of 1" I should be able to cope with pretty much anything that's likely to happen. I hope!
I guess now I've got what I'm building sorted I'll have to do some head scratching and work out exactly how to build it..
Still not looking forward to drilling holes in the glass though!
