Originally Posted by Tuomo
In practise I probably have plenty more stability in launch than in normal or thermal flight modes. This is due to launch camber.
But please elaborate. I think the method described is very common among F3J/B flyers. And sensibly used, it leads to modern middle of the road F3J launch trim. I learned it first from F3B community where the pilots seem to follow it very rigorously, ending with hook more rearward position than what is common in F3J.
Overstability in launch is generally bad, it causes oscillations which cause the plane to overshoot the optimal angle of attack and enter a pre-stall condition. To overcome this you either use your thumb or settle for a less than optimal trim.
Reducing longitudinal stability via the towhook position is an easy fix. A plane like the Supra also gets some residual stability in launch from the pylon-mounted wing.