Stop! Don't ruin your rod. Standard fighting butts have a cross cut / 90 degree cut channel to seat into a fighting belt receiver or "gimbal". The cross cut mates with the steel pin within the gimbal for a positive lock. This pin prevents non-fighting butt rods from fully seating within the gimbal. On some belt models, the pin is removable to allow rods that don't have a fighting butt installed to be fully inserted in the gimbal. Buy the belt, save your rod. Check out Meltons or another other blue water shop:

http://www.meltontackle.com/products/aftco-fighting-belts.html

PS - the only two reasons for a fighting butt on a fly rod are Ahi and JC's. Take me with you!