I went through the same deal trying to hang my radion
I was trying to build a sliding rail system and only found the closed square tubing at Ace; affordable enough, but yea, didn't want to try to cut a slot with a dremel...especially since it wouldn't be hidden by the hood.
I'd still be interested in trying to hang my lights on a rail...and might have a connection to a CNC shop. Lemme know if you want me to get in touch with my friend to see if I can work something out...not exactly sure how I'd build mine, but if all you need is a nice slot cut into some square tubing that should be a small enough favor to ask him.