Because that exhaust pipe exits upwards, you might need to get creative. We use a Whizzer-style flex pipe on ours. The stock pipe and muffler was cut off about one and one-half inches above the flange. The flex pipe fits perfectly over the stub, and is locked in place by a one-inch seat post clamp. We have it exiting out the back under the rear carry rack. Because it comes reasonably close to the seat, we wrapped it with exhaust wrap to minimize the possibility of cooking the inside of one's leg.
When RusticoRay had an HF engine on his cruiser, he also used the flex pipe but routed it forward and down. I've attached some photos. One shows the our bike before the exhaust wrap was put on, the send shows it with the wrap in place. The third shows Ray's bike (the yellow one) at the end of the lineup.
