Thanks, that helps. So there should be no problems with rimless on a tank that size?
I live in Portugal, locally the cheapest 5 gallon tank I found cost 40 euros and it looked tacky and badly made, one I liked (but not particularly fancy) cost more like 70 euros (it was a kit including filter etc, but I already have those things. I think those prices are just silly especially because I can get a 20gallon for 30something euros in the same shops, but I've looked everywhere and just haven't found better.
It also got me thinking that if I do it myself I can have the exact measurements I want, which would be handy. I have the silicone already from fixing another tank (it only cost 5 euros) and the glass will cost about 10 euros if I get it cut, if I decide I'm brave enough to cut it myself I probably have enough sitting around for free. Even if I find a 'cheep' tank it's going to cost me more than that.
My biggest problem has been finding information on making small tanks because it's not worth it for most people.