Stability During Acceleration...
Trying to direct/control a rocket with nothing more than a balloon, string, and rod sounds like the beginning of a bad joke: This balloon, string, and rod walked into a bar...lol
The rocket and launching rig should make a clean separation. The rod is likely to cause more issues than solve.
The rocket needs to be inherently stable during acceleration regardless of how you launch it. This means the CG needs to be aft of the thrust. Put a long rod on the tail. Drop the rod for the glide home.