RC's do not have overload springs. The leaf pack has a "slapper" leaf for traction. With poly leaf bushings and a larger snubber to "preload" slapper, traction is improved significantly. However, there is a trade off in suspention compliance. The ride out back is stiffer and can "bounce" over road irregularities. This can reduce confidence and stability in the rear of the truck though bumpy curves. Big snubber bushing is great at the strip, bad on the street. Re; the trucks "rake". Low looks "cool" and there are benefits to a lower center of gravity. If the truck is lowered, you will also need to correct the sway bar links to keep the ends parallel with the ground. Lowering the back to "level" the truck WILL have a negative aero effect. A "slight" rake will create a low pressure area out back, under the truck. As the air comes under the front splitter, past the chin "tray" underneath the front, the air will then GRADUALLY expand and slow down as it passes towards the back end. This is where the low pressure area occurs and creates "suction" which pulls air through "faster". Take this slight rake away and the truck will slow down and loose top speed. So, when lowering, keep two things in mind. Keep the slight rake AND be sure to maintain travel. About 3" up and 2" down to keep compliance for road irregularities. Otherwise, when you push the truck, it will bounce and jounce you into a ditch!! Cheers!