They seem to be just nutserts, so I would definitely expect them to leak. I did the silicone on mine. One thing I didn't do, but probably will at some point is get some regular pan head screws. The ones for the rack have a stand-off part for passing through the rack. The screws will stick up from the roof about a 1/4" or so.

Big Truck: 00, 3.5, Endeavor, 5-Spd drive line in hand!
Little Truck: 87, 2.6T I/C, MT, LSDs, Tonneau Top
Her Truck: 03, 3.8, 20th Anniv, 65k
Daughter's: 06 Eclipse, Keeping it Mitsu!
FSMs: MitsubishiLinks.com