RF, you thinking more along these lines....?
Shovelhead FLH rear fender, held on via a 7" side mount headlight bracket. You can get the bracket at any shop that carries Custom Chrome brand parts, you may need to look in the Jammer's Handbook.
The chrome thing you can see (barely) between the seat and the bags is the fender bracket. Bolts on the frame, fender bolts inside the bracket. You'll need to make a set of lower spacers/mounts or use the tail pipe as the rear brace (VN800 reflector bracket).
You could use a hinged rear fender but you'll need to make some structural side rails to tie into the main frame cradle.
If you want the full fender to pivot, a couple brackets on the swingarm, rods mounted to the fender, use the headlight bracket as above.
You guys building bobbers... you can get a "Fat Bob" type trailer fender as well... about $30 at Tractor Supply.