Tinkerer -1, back seat - nothin'. After finding all the secret hooker snookers that held the back seat in, I wrestled it free. The fuel tank on the other hand fought me all the way. The hold up straps wouldn't give and I had to cut them. This led to the tank coming down at a tilt and spilling about a square yard of fuel on the floor. I had to scramble to shut off the heater and open both doors. Then after soaking up the spill with sawdust, scooping it up and rinsing the floor, I started on the fuel lines (of which there must be a dozen) and filter(s). Each object had another half cup of gas to dribble. 20/20 hindsight says find a way to totally empty the tank and complete this task out of doors. Having no witnesses to the contrary I will call it a draw.
I sorely miss the tools I had available at work, before retiring. I bought a small welder, auto darkening hood and accessories and an assortment of abrasive cutoff wheels. These will be used to build the battery containment frame. Of the $220 spent I will post $110 against the project.
An idea has just come to me; I will use the rear seat belts to secure the battery box cover.