That´s right, toptubes have to be extended like 5-ish cm. I also put a smaller tube inside the extension point to add strength. You just have to find the right point to cut the rear diagonal tubes to manage with 1 welding on each side but you can do 2 on each side too. I wanted to keep the original bend in there because one straight tube is too boring. And you can always cut it and mark the new higher spots on the main frame where the extended subframe should connect and have it made in a weldshop, it´s a peace of cake really for a welder.
Sure you can use a gel battery, no problem. And don´t spoil your mood with the wiring just yet, it´s the last thing 8)
Anyway, yesterday cruised around the city with my lady. This 1,5 person seat is totally ok for 2 person cruise. The bad thing is that she got to like it.