A lot to catch up on here, so in my quick run through, I’ll try to cover what I retained while speed reading.
If I missed any specific questions, please ask again.
Stay far away from FOA. Junk total junk. The list of issues is too long to list. ManF is junk, assembly is garbage, QC is non existent, customer service is on continual vacation.
It’s not just the seal material... seriously, stay far far away from FOA.
Profender is a very nicely built imported shock that has American support in PA. The guy that is in charge of Profender NA is a great guy that wheels and stands behind Profender. Easy to get in touch with and get fair solutions to problems. I would run them. Only reason I personally don’t, is getting a good assortment of valve shims to really tune them.
Ok the load/weight capacity on air shocks. Yes it’s there for a reason. It has to do with seal layout and design. Stay below the max weight recommended.
When you charge an air shock, it is a sealed chamber. It holds the weight up because the displacement of the shock shaft causes an increase in pressure to hold the vehicle at ride height.
When that same shock is fully compressed, the pressure inside the shock increases dramatically.
If you are over weight capacity , which will require more initial pressure to set ride height, and then compress the shock, you will likely push a seal out, damage the seal head, and lose the n2/oil charge. That shock will then require full rebuild.
The valving doesn’t affect the compression ratio inside an air shock. Two things are at work in an air shock.
1) The compression ratio based on oil volume and n2 pressure : sets ride height and is the spring force, and also is the “built in bumpstop”
2) The valving that is the damping of the spring force: handles the dynamic movements not the static positions.
TLDR version: FOA bad, exceeding MFR weight capacity on air shock = very bad.
@Marty John For what you are describing, I’d be looking into some 2.0 emulsion coilovers or A separate spring & shock combo, like the JK spring and shock combo mentioned above.