Patch panel behind seat riser fits nicely and accomplishes what it has to - reinforces the floor and ties seat riser into the floor. I've decided to rivet this instead of welding. The floor is pretty rusted and I'm not sure how I could have secured the patch without fasteners spread across the length and width. None of this will be visible unless you pull the seat but that doesn't mean I can scrimp here. Solid steel 1/8" rivets are more than adequate and years of driving rivets on aircraft, I can attest to their strength.