I used bolly large swept gear attached to the fuse. The icepoint gear would also work.

I cut the balsa plate off just in front of the former the wing plugs into. Ran a rail along the inside of the fuse flush to the bottom and glued and screwed 5/32 ply to the rails to reclose the area and create a gear plate. Drilled it for 1/4-20 nylon bolts and screwed the gear on. Then cut a slot in the chin cowl to go around the gear. I have broken the nylon bolts twice but the fuse held.

I have a 2nd JR Explorer still NIB, If I ever put it together I won't even cut the covereing off the wing for the retracts. Closing the holes back up was harder to do than installing the fixed gear to the fuse.

Now the Excelleron has some vertical stringers that I didn't think to do but agree it would add stiffness.
Eddie