What is your height? This is a dumb question maybe, but did you double check the tighteness of all the bolts attached to the springs? Also, the difference in spring can "sometimes" be attributed to a difference in leg strength. If you really don't like them, and it's been under 90 days, and the seller won't help you, then if you used a credit card company, tell them you are disputing a charge on product not as advertised.

If you are in the US or N.America, since you have up-wings and there are no licensed sellers to the US, if the weight and tilting foot plate is a priority, but the calf calf is, then the 2007 poweriser (with an s not a z) are probably the model you want. But you will need to make some mods if you are under 5'6". There are some good ideas at these websites : powerbockresources.com/ and www.poweriserpages.com/ . If you need confirmation of the seller's website, you can use this link www.xtremeimportz.com/UP-WING...rs.html. I would take a screen shot of it, just in case.

Hey guys,
We ended up with used M80's instead of Upswings for several reasons.
*Price
*some desired MOD's were already in place
*Based on the good faith relationship I had already established with the guys at Powerrizer.
*Known quality of available next-gen upgrades.

I am am a whopping 5'0" tall with an equally small foot. = short shin (shins constantly got banged and bruised) and poor foot support (feet were constantly sliding around)
Part 1. As for comfort on the knee bar/calf straps - The original bar is a terrible design, I did everything to make adjustments. Ultimately, I have been most comfortable with the '07 upgrades purchased directly from getjumpingstilts guys. This included the advanced calf cuff and advanced bindings. I just spent 5 hours in a parade and was completely comfortable in them.

Part 2. Ordered a used second set, this came preMOD'ed with ski board foot bindings - which seem to be equally as comfortable and stable. Next I am going to attempt to MOD the existing knee bar by cutting the front out and riveting heavy duty leather as a calf cuff.

So that's the story at the moment - Lessons learned: The calf cuff changes the wieght placement on the stilts to where it should be creating a more "leg like" feel. The foot bindings are a lot more secure, adjustable and comfortable.

That's my .02