Thanks for the replies. We have been busy with our first grandchild's birth the last few days. As far as the arms being different lengths, they are the same and I first tried the two bar clamp idea to compress the spring and couldn't get it compressed enough that way so I called Little Giant and they suggested the ratchet strap. Like I mentioned the hammer seems to work okay with the old spring I just wanted to replace it for safety. I actually am not using this hammer and plan on selling it so I'd rather avoid making new parts. I was hoping someone would say, "oh some machines just have a 7" spring" and I could cut the new one down with an abrasive saw. I agree with Beaudry that a longer spring just makes the problem worse because when I tightened the old spring the hammer didn't hit as hard. I am still open to other thoughts.
Thanks Todd