Mini Catapult - Supports for the base

I printed this cool mini catapult by ATECH:
http://www.thingiverse.com/thing:438870

The result was awesome, the catapult shoots great distances with good precision, however I noticed that the thin base tends to fold up when the rubber bands are fully stretched (to achieve greater distances).

I decided to add two supports on the side of the base, and I included diagonal slots on the bottom part of the rails to make room for the rubber bands, so that the whole catapult is flat on the groun