Leaf springs, modify for extra separation on launch?

I am thinking that it might be possible to add a modified leaf above the main leaf to increase rise in the rear. This car is a 65 Dart, will have a 500 plus hp Gen 3 Hemi of 392 cubes in it and will need all the help it can get on the street. That means lots of chassis rise on both ends.
Has anyone tried adding a partial leaf to the springs, above the main leaf and with the rear half cut off, clamping the front to give the springs mopre bias to the front? I have a set of stock rear leafs off another 65 DartI would like to try this on. The 3400 lb SS springs I bought are so stiff the car just lights up the tires, and all it has at present is a lowly 318!