Zadwit, if I read your question correctly, it sounds like you are having problems with the spring suspension bottoming out and bending the gear. Aside from learning how to make smoother landings, it appears you have a couple of choices:
1- To get more travel without remodeling the spring mounting collars, you could reduce the number of coils to get more space between coils, but that would increase the load when the spring finally bottoms, putting higher load on the gear. In addition the spring wire diameter would need to increase to handle the higher load.
2- You could keep the same number of coils but reduce the wire diameter to give more travel, but that would allow the spring to start deflecting at a lighter load, probably not desirable.
3- There are some other possibilities, including trying some different spring steel alloys that may offer a better compromise, but I don't really think anything is going to give you enough extra travel without major load changes to make the difference you are looking for.
Probably the best solution is to remodel the spring mounting area to allow a longer spring to be installed and/or add shock absorbers, or bigger softer tires.