From the point of view of righting a capsized boat, the fixing of the jib tracks on the seat does give me some concerns. Despite my being more of a cruiser than a racer, I too have fixed the tracks on the seats, in fact on a hardwood batten that sits between the slats and bolted through; I am happy that the tracks will stay attached to the seats.
I am not so sure about the seats staying attached to the hull. The image above is of a MkII identical to mine where the aft end of the seats are bolted to the thwart but the front end of the seats rest on a ledge formed in the GRP bulkhead. The seats (on my Wayfarer) are held down by round-headed screws that slot into grooves cut into angle (looks like plastic but could be painted aluminium) bolted below the seats. Different Marks have different arrangements.
I am concerned that the pull required to right a capsized hull, if using the sheets as a purchase will be imposed on the fixings that attach the seat to the bulkhead and I am not sure I trust mine under this sort of load. So I will be strengthening the connection between seat and bulkhead with this in mind. If the tracks are fixed on the side decks the righting force would be applied to a much stronger integral part of the hull.
How are the front ends of the seats on your Mk II attached?