I may be stating the obvious, but I didn't see what kind of punch you are using, I hope it is not a standard pin punch, but one designed for roll pins, they have a "nipple" on the end designed to push the center of the pin in and release the tension (why you use this type of pin in the first place). I am a NF guy, so not familiar with a 108, assuming it is similar, but easier to get to. I purchased one of these:
http://www.ebay.com/itm/Punch-Roll-P...item43cbba0e28
It is long enough to reach through the creeper hole on a NF and whack it from the top, may not be a Snap-On, but is USA made and I have removed many pins with it so far and no problems. Once you get it moving a pin punch usually works to finish removing the pin.
Good luck,