I think you need more arch than pictured, to give yourself a more favorable king pin angle and mitigate shimmy. Your current spring is flatter than it's intended design, so there isn't any drawback to getting it back to conformity.
Talking about lengthening the spring sounds like a redesign/structural question. It's probably not ideal to give it more leverage against the fuselage and its mounting points. This whole area was designed as a system and it gets some hard usage.