Here is what works - if you really don't want to mar it at all - or bend it.
Find a wooden dowel that fits inside the feedneck snugly. I made one for this purpose alone. It is just a wooden plug that is the size of a hopper neck (Around one inch - or about 1-1/16" inch.
Insert this plug, tighten down the collar with the 5/16th allen key - then use a strap wrench.
If you can - warm up the connection of the feedneck to the body with a lighter before doing this - this should loosen the red loc-tite used.
You should be fine with this.