Pondering these issues myself. Can't see that a 1/4" hole on the batter side of a 26" bass would make any change in sound. Looks to me that LED rope lights would work fine. Makes far more sense to run the wiring through the head than drilling the shell.

Per painting heads... Dusted off the lighted image projection device. Will work fine. Just hang the head on the wall. Project desired image, pencil in the guide lines and paint away. The cheap ones just were placed on a image and project same. Much fiddling with focus/distance and such.

Found a pro grade for $15 on CL. Focusing glass lense. Can really dial in the detail. Regret device is 1600 miles away at this time so no pics.

Creighton