It is one of the more frustrating jobs to get accomplished on the bike, so simple, but yet it just doesn't want to co-operate .
Warming it up might help .
My last time doing this, I tried compressing the pleats on the boot, with very thin sheet metal (.005 in thick) wrapped around the boot, secured with a couple of ty-wraps, it compresses the pleats, and makes the boot expand a bit in length .
Worked for me, no telling if anyone else would have success or not .