Looking good. With regards to your power cable termination, I would find the appropriate spade size with the largest gauge body you can. Then strip back an extra .5" and cut the strands to fit. Slip over a piece of shrink tubing, crimp and flow solder, heat the tubing to bridge the insulation, bare wire and spade. Since you are firing into the moveable floor, I would make sure you have the accessory floor mat that can fold to further weight and damp the floor. Since this design is effectively a bandpass one, the risk is for the bass to be "one note" and restricted dynamically (either on or off) due to the mass loading of the air spring in front. Should this be the case, you have an acoustical tuning capability allowing you to reduce the size of the "port" by framing the woofer on one to three sides attaching the frame either to the floor or the woofer cabinet.
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