I used Silicone around my gearlegs when I built my Defiant. I ended up with a delamination over the gear opening on one side, due to the flexing of the gear pushing the silicone which pushed the outer skin of fiberglass. I had left about 3/16" clearance all around, and filled it with Silocone. It wasnt enough clearance, and it was too much sealer. After fixing the delam, I opened up the clearance to more like 5/16 and just put a thin gland of silicone over the opening to seal it.
Harry Manvel
Defiant N2HM
PTK / Pontiac, MI