I just had to do it. Against all odds.
I doubled up the rubber.
Now we are talking!
The stronger bandset pushes the weapon into the realm of deadly weapons. The pencils now go through a rubber door mat, which withstands the 20 mm steel ball hits from my strongest slingshots!
As a matter of coincidence, some better quality pencils arrived (Faber-Castell HB, 1,18 Euros for twelve pieces including tax). Much more solid. Just in time.
But in order to push the envelope even farther I took a damaged carbon fibre arrow shaft, sawed it into five pieces and glued tip holders in. Then I screwed the field tips in. The arrows now weigh 9,6 gramms (154 gr).
The impact is absolutely astounding. They go into a massive wooden plank and I need tools to get them out again. They even pierced through a PET water bottle and still stuck in the plank. Distance 8 meters, the flight is absolutely stable.
I reinforced the string catchers (glued in a steel nail in fact), so the weapon withstands the much harder impact of the 300% pretensed bands (3,5 cm x 2,5 cm x 11 cm relaxed length).