has anyone used one of these kits?

[randyjohn]

http://store.summitracing.com/partde...5&autoview=sku

these Firestone kits are out of the Summit catalog and are helper spring kits for chevy/gmc pickups (there are several other kits for vans, burbs, 4x4, etc.). i was wondering if anyone had experience with them or knew pros and cons of them. i want helper springs for my 3/4 ton so i can have load and lowering capacity. i like the price and seem to be an easy bolt on. i'd have to ditch a couple of leafs (i have 9 now) to be able to get down a bit but i was unsure if they would work with lowering shackles and hangers. i doubt i'd have room to mount the upper bag mount on the frame but i'd like to hear from others.