Ok, here we go. Right from the outset let me give credit to Mickey Coggins (http://www.rv8.ch) whose website helped me find a solution to the problem of mounting the Andair fuel selector. In the photo you can see what I hope is the final solution. Using a flat plate of .063 and the original fuel selector bracket I have moved the Andair forwards and more central which gives (hopefully) plenty of clearance for the various tubes, though it will still be a tight squeeze given that it is a duplex selector and will have fuel return lines.
I think the only difference between my installation and Mickey's is the additional angle support for the mounting plate at the front. The Andair fuel selector is quite heavy and I felt the extra support would be useful: it is simply a piece of .063 x ¾ x ¾ angle. I have had to shape it slightly at the inboard end to fit around the existing nutplate on the mid cabin brace. A nutplate will be installed on the underside of the angle at each end and I'm thinking I might do the same for the original bracket rather than use nyloc nuts. The .063 mounting plate will be riveted with flush rivets to the two brackets to make a complete assembly. I still have to make some slots, reliefs or cutouts on the angles underneath to allow clearance for the various pipe fittings, but I'll do that once I work out exactly what fittings I'll be using (I ordered some various fittings from Aeroware so I can have plenty of options to play with).
The F-844 auxilliary longeron and the mid-cabin brace will be countersunk to accept #8 screws. The cover plate will, of course, go over the top of the whole lot and will additionally be 'clamped' by the Andair cover plate.
