I've found that silicone (RTV) of some types can be unreliable when using it on a thin piece of sheet metal. Gaskets can be better, but for the inexperienced, can also lead to problems. If a piece like this is over torqued when using a gasket, it will end up getting warped, or cupped at the bolt holes. One of the best sealants is this stuff...
http://www.magicracing.com/ThreeBond...1104_p_84.html I've been using it on bikes, cars, and ATVs for years. It's good stuff. Most motorcycle shops will have it in stock, and swear by it.