I have searched but all I seem to find are threads for the sale of these fins. What I need is a little help with an adjustment. I have a set of medium fins that fin great the problem is the OEM backstrap. It's to tight. After a half hour or more I can start to feel it. What I need is a set of springs or maybe a set of large backstraps??? Anyone else run into this problem? I love these fins because of the amount of energy return you get.