My advice would be not to lay the seat back too much, as the head restraint then becomes useless, so if you have a rearward impact, as I did you will appreciate a well mounted seat. I dont know how you get around this probelm but I would be trying to lower the seat another way. Have it standing upright as much as possible.
If you mount the seat directly on the floor as Jonny Rochester said make sure you support the mounts from underneath as the floors are quite thin and could easily tear the bolts through, in an accident. You can do this with some steel plate to spread the load.
