Challenges are making sure I can get access to the battery box / battery, Gear selector and the brake fluid opening. I did a lot of mocking up with different seat heights, lengths & angles. There is not a lot of room in a T-Bucket to even 10mm makes a difference. Finally decided on the length and just enough height to clear the gear selector.
The picture above shows testing where the steel sub-frame would end. The wood based seat will over hang the frame about 50-60mm. The seat base will be 18mm marine plywood.
Rails and cross members mocked up. The bottom rails sit above the chassis rails, wanted to make sure that no flex was present. Front cross member raised 50mm from floor, while the rear cross member is flush to the floor.
The whole of the seat sub-frame will be hinged off the 25x50 box section that the seat belts are bolted to. This cross member is bolted directly through the floor to a corresponding braced cross member directly below. The hinging allows for easy access to everything under the seat.
Picture of the clearance of the sub-frame from the gear selector, The selector is in reverse. In this position the selector is in its highest rear most position.
This picture shows the 3 top diagonal rails welded in. this is what the seat will be mounted to. The triangulation also adds to the rigidity.