Aftermarket bucket seats into a bench seat car- concerns and considerations?

Recaro seats here as well.
These are 11 way adjustable newly recovered out of a 91 BMW 3 series car.
It is kind of a challenge to fit a non flat floor of an A body car with seats made for a flat surface.
I opted for building frames to adapt the two together using the seats OE equipment sliders and the frames varied heights to the floor (different heights on each corner)

I considered a one piece frame all the way across (which could have been easier)with a center I could build a console/cup holder between the seats, but ended up doing a separate frame for each seat.

Each of the four corners of each seat is reinforced with 1/8 steel plate 3x3 inches.
Not welded, but may be in the future.

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