Hmm I'm similar size but have the problem of the roll cage so with them leaning back it was touching the cage.
I also found the original seat mounts to be quite flexible and seem week as I think the standard seat sit in the rails rather then on them.
All you can do is have the seats out get the rails and see what you can do but I think you would w better buying the proper subframes if all the interior is still in place and you want it safe.