I`m piecing together a 26 rpu. I have new seat springs and am waiting on upholstery. Does anything go between the spring and seat riser? It sseems there should be wood or something as the spring is not stiff enough to support 2 people.
I put a pc of 1/2 in plywood, and paint it body color, leave a finger hole to get it out to put fuel in, and install springs on top of it, I weigh about 270 now, used to be lots heavier.
The seat spring was actually attached to a wood frame. I have a seat that I can take pictures of this weekend if you can wait
I`m in no hurry.