However all the tightened straps pulling up on a seat track mounted to a few floor beams might be something no-one has ever thought about.
Each seat track notch is rated for 5000lbs of tension. It does not matter how many straps are attached to the seat tracks, so long as no single strap generates more than 5000lbs of tension. Exceeding 5000lb may cause the individal seat track notch to fail. Each notch has a 25% margin designed in when new. But the seat tracks take a beating, so there is no guarantee the 25% margin is still there after several flights.
And BTW, preloading a strap places a preload on the individual notch of the seat track, but does NOT preload the seat track to floor beam interface. The floor beams only see the maneuver/gust loads. Think of sitting in a chair and grabbing the seat bottom and pulling up. That places no additional load on the chair legs. The chair legs see only the load of the occupant's weight.