64 mm is the correct size.
Without knowing which side of the bike your attacking the filter from may I suggest the following.
If your using a cup style 14 flute cap in the correct 64 mm, and its slipping, try a small piece of sand paper in a couple of the flutes, or lapping compound.
I'm not one to bang on stuff with hammers and punches, so I'll try and offer you an easier approach.
Remove the lower RIGHT side cowl (black belly pan) to gain access.
Now you'll have a full throw on your ratchet or breaker bar from the ground up, pulling towards you. This alone will help alot.
You may want to spray on some PB blaster, or mix up some Acetone/ATF fluid in equal parts and soak the base of the filter.
Resist the urge to Yank, Jerk, Hit or hammer on the filter.
Instead get everything lined up, apply increasing pressure, then wait...don't let off the pressure. 99% of the time, after a moment or two the contact will give in and you'll be able to spin it off.
If you can't get at it with this method (on the side stand by the way), find yourself a blanket, cushion, or tire, and gently lay the bike over on the left side (this works on PD bikes often).
You will now have more than enough room and reach to grab the filter with a large set of oil filter pliers.
Hope this helps.
Igofar