Is the gear aluminum? If so, then I wouldn't try to plug them--I'd just re-drill some holes that will allow the 1/4 X 20 nylon bolts to slide through. then, drill into the block of wood inside of the fuse (using the gear holes as a pattern), and install some blind nuts. All should be good. Really, this is a no-brainer mod. Don't make it too difficult. Just make sure the gear block is sturdy, and is tied to the side doublers with some triangle or square stock, epoxied in. Other than that, make sure the axles will line up with the LE of the wing, and don't forget to re-balance when you are done!