I reckon you'll find that a lot of American big V-twin engines have historically been supplied with charging systems that are rated for about 26A with uprated stators being available that give about 32A so 38A is not necessarily "wimpy" except when compared to large car type alternators that are hidden under the bonnet and really quite large. Bike alternators tend to have a rotor directly on the end of the crank with the stator bolted to the inside of the engine cover. With the engine being on display this cover is a bit on the decorative side rather than just being a weatherproof cover and it definitely limits the size of the components inside. Sorting out a location for and a drive feed to a second alternator could be an interesting challenge.
Apologies if the technical terms aren't quite right...not an electrical engineer
I just don't want to end up in a situation where I have done a long run in proper cold while nicely toasted by a heating circuit only to find that the car won't start next morning because it has been slowly running the battery down.
