The Sumatra Canon was so powerful that even the shell of the tough Prana Bomb shattered after a kilometre of flight. It hadn't even impacted upon a target.
As long as Inala continues to train and progresses in the Body Stage, the toughness of his Prana Bomb will continue to increase. Soon, it would be able to withstand the force of flight and impact the target successfully.
As for the recoil, as long as he strengthens his Secondary Nature while making a shot, he would be able to withstand it.
Sumatra Canon was no different from a powerful canon. He was satisfied with it, for it would serve as his trump card. Moreover, as it had been stabilised using a Sumatra Gold, the space within would maintain itself without issues.