All of the ships are made out of paper thin, hallowed out aluminum girders (even the wood, its just painted wood color/texture) and the balloons are already filled with hydrogen. Using hydrogen canisters just hyper-inflates the balloon to get an altitude boost. The following balloon damage is caused by small tears in the hyper-extended fabric which leads to you losing altitude shortly after the boost.
The Mobula is able to prevent itself from dramatically flipping upside down by being filled only with the methane of Skywhale farts which has amazing self-stabilizing properties.
It works if you don't think about it.