I bought two springs that I thought might work, after some head scratching I think they might be way too stiff. After some more head scratching I thought what about bungee cable, the only purpose of the springs is to keep the pedals from falling backwards. After A search on the old forum I managed to find one thread of someone using bungees he said he removed the metal hooks and looped the cord around the attachment points and clamped the cord to itself with safety wire. This sounds like a better method to me, you save a little weight and the tension is easily adjusted.

Hi.

I couldn't find springs that fitted either, so I used bungee cords. They work just fine. I used the metal hooks, but shortened the bungee cord, to get sufficient tension. See picture.
Edit: I see now that you build a Hi-Max, so this might not work.

Petter

Thanks petter, it should still work, the spring on the minimax/himax just works in a different direction.

The spring serves no function other than keeping the pedals from falling back when you aren't in the plane.  They don't do anything once you are in the plane with you're feet on the pedals.

Nice clean looking mod on the rudder pedals Petter, if you have long legs, you will find that to be much more comfortable than the stock location.

Paul Fiebich