One cheap trick, is to clamp a section of a leaf onto the front half of the springs. This strengthens the spring, in that area and helps to prevent it from flexing, or bowing up.

Then there are the old school slapper bars. When adjusted correctly, they work OK. We won lots of races using these. I built some cheap ones by just welding a piece of square tubing to the shock plate, and adjusting with metal wedges and grinding the snubbers.