I have a lot of weight in the back of my fit, probably about 600 extra pounds of stereo equipment, (mainly 5 group 31 batteries!) I have 16" rims and they are tucking in the back with everything in, are there any companies that make heavy duty springs or helper bags for fits? Anybody else have this issue? I've already had to upgrade the brakes because of the weight

 

 

Swift springs. You can order custom rates and lengths.

 

Some people have used Monroe air shocks with success; you can search the forum for details. At least on the GE8, there was no exact fit, but there was a model that required only very minimal fiddling/shimming to fit properly.

By the way, your batteries are not connected in a balanced manner, so won't charge and discharge precisely equally. Over time, this can lead to extra battery capacity reduction and other undesirable effects. Perhaps in your situation it's more a theoretical difficulty than an actual one (as your battery interconnections are pretty low impedance).

 

You can get springs in whatever length, diameter, and weight that you want from eibach. They are about $55 each.