At 5'7" I have the same problem. I wouldn't suggest the spacer. Instead go ahead and have your foam shaved. I did this on my 2000 KTM 125sx (i used a hacksaw) and it was like being on a new bike. Also, on a KTM such as mine, you can saw about a 5mm chunk out of the sub-frame and it will lower your ride about an inch. I haven't needed to saw my sub-frame but KTM claims that if you do, the rear wheel still won't bottom out. You can do the seat yourself, just be sure you have an ample stapler for the seat cover...hand operated staplers won't get the job done, you need an air gun.