A backside view of the front filler post. Front is 3/4 pine backed with a post, screwed and glued in place.

At this point, I decided to cover the battery tray area, but you don't need to.

A view of the T-nuts used to hold the seat panels in place. 4 holds the seat bottom and 2 hold the seat back.

Plywood seat panels cut-to-fit and provide something to staple the cushion and vinyl covering to.