that's a great mod
I used a speargun tip thread converter, 5/16"-24 to M6, to let me make a modern bicycle lamp bracket for the standard threaded fork lamp boss on a 1957 Raleigh Lenton.
building bicycles is one thing more fun than rigging kayaks
Josh, you've mentioned elegant - the elegant approach would be using a plug tap and counter-bore to match the arrow point threads - they would be easily replaceable, and the o-ring would probably keep the threads from backing.
Even better might be embedding the bore with a matching EZ-lok stainless thread reducer.
EZ-lok are kinda like helicoils, except you don't need special tools other than a matching major thread tap - you can drive them in with a slotted screwdriver.
Here are Harmony track nuts I converted to 8-32 using EZ-lok