progressive rate spring for 130 series surf?

[NA_Drifter]

Does anyone know what brand and where to get some rear lifted springs with progressive rate for 130 series surf?
I have check that King Springs, Dobi, and Cobra haven't got progressive rate.

Reason is that, is not carrying weight most the time, so it not bouncy but in the odd time it will be loaded up and towing.. so I just don't want it to bottom out like it normally does.

Thanks

[SupraLux]

The ones I carry - Maxitrac - are a fixed rate as well... I think you're only options there might be to use either a standard spring with air shocks (the old school air shocks - pump em up to help load-carry) but that makes the ride quite shit and they are expensive these days... or you could get poly-air springs which are a similar concept but they are a big air-bag that sits inside the spring and you pump them up for load-carrying. Not sure how they ride or affect handling.

Or just get some new coils and some decent shocks and put up with it sitting down a bit with a load in it.

Steve