I have not cracked or broken an OEM seat support, but I did get wear in the track and on the ends of the supports. I liked the ease of changing my set up with the OEM supports, but have gone with a fixed mount instead. My console bench, the seat bench and my ski pole are all attached by bolting to backing plates in the hollow floor sections. The backing plates extend out to the very edge of the floor. When the floor is assembled these plates effectively key into the the locking rail making a very strong and secure attachment. The seats and console just attach directly to the backing plates. For the gas tank, battery and ski pole I attached a plate across the floor first. The thin floor top sheet just wasn't going to work for the loads applied.
The system isn't as easily changed, but I have pulled my fixed mounts for a special use that needed clear deck space. It was a pain and I plugged the bolt holes while the mounts were removed. The best thing about the fixed mount mod is that the space under my console wasn't taken up by the support braces. I raised the console a little too. Gas tank and battery are stashed underneath. The floor space below my seats is also wide open. Great place to strap down dry bags.
Clearly not for everyone, but maybe my application will give you some ideas. Picked up the aluminum c beam as scrap from my local Industrial Metal Supply (like a candy store for me). My top end speed may suffer, but the vessel is very useable for my applications.
This is one of the seat supports in place.
A view of the backing plates in the hollow floor sections for my ski pole mount.
Not the thing to do if you aren't trailering your boat! But sure opens up the deck space (with gas tank and battery out from underfoot) and the mounts hold up to my suspension seating.