How to make a custom seat:
Step 1: make a cage and an under tray to hide your battery and other electronics. That way your passenger doses not crush them with their butt or have their taint zapped
Step 2: make a template for the height / curve of your rear cowl
Step 3: Duct tape…. Lots of it pulled tight over everything. This will serve as your plug to fiberglass over top
Step 4: make a bracket to bolt down the seat by welding 2 bolts to a piece of steel. This will get laminated between layers of fiberglass
Step 5: Fiberglass, fiberglass, fiberglass. 3 to 4 layers. Pay attention to edges and cross match the grain
Step 6: let dry, pop it off the bike and trim out our seat pan.
Step 7: play with foam shapes.