hey oh zone, do you mean the channel betwen the inner liner and the outside of the seat itself ? if so, thats all been replaced with new hardware and is secured . thanks Rick

No I mean a support brace mounted externally. It attaches to the outside back of the seat approx in the center then a 45 degree angle to the hull side Mine were located in the black portion of the bolster not visible though in this pic

Here's another pic. on the back of the port bolster you can see the support brace

It keeps the seat from twisting which is what I believe your seat might be doing thus dropping the bottom. Thats what happened to one of my seats when the screws were not tight....

thanks oh zone, yes i have the rear support braces in and every thing is good and tight, i've adjusted and realigned everything several times, still no workey, it usually is the passenger side that takes the beating in rougher water, it does'nt happen that often, but it sure scares the hell out of the passengers when it does. thanks Rick