The Bostrom seat came with an optional tilt plate to allow the seat to tilt forward. Essentially, you remove existing LR seat, & rails, & the seat box cover. The tilt plate is hinged to the front of the toolbox/battery box, and the seat rails are then mounted to the top of the plate. Easier to do than explain.
The hinge pin is one, long removable rod, so you can lift the entire seat out, which makes life easier if you're replacing the battery - else the seat, tilted forward against the windscreen, didn't quite give you enough space.
I fitted the optional second fuel tank instead of the tool box in one of my earlier Series.