It occurred to me that you may be planning on using the spar as a mount for a fuel selector valve (which I would also leave out...but that's just me). Even then, I'd find a different way to mount it, such as reinforcing the web with another small piece of 3/16" plywood locally, or an angle bolted with about three #8 screws to the web and/or spar cap. I have dual wing tanks on N56ML with no selector or "off" valve, and that has worked quite nicely...never hiccuped a single time for lack of fuel except once as a test...when I deliberately allowed one tank to run dry to see how it would recover. Recovery was almost instant, so it was a non-issue.
Mark Langford ML at N56ML.com http://www.n56ml.com
