I've felt that the problem with the mirrors is not their size but their positioning - for me at least either the bars need narrowing or the mirrors need moving up and out. I bought some longer screws today - and was about to start carving a block of wood when I noticed that the two screws are not in line.There would be enough grief making a 2" thick piece of wood fit the (slightly) recessed piece of the fairing, plus there's the countersinking to fit the fairing mounting screw (shown) and the "plugs" on the underside of the mirrors to take into account, and now there was the need to line up two non parallel holes - as you can guess, I was losing interest now.
It looked like a Homebase visit was required. A 
Ferarri F430esque solution using the copper pipe as a spacer - I thought I might need to run some nuts up the threads inside the pipe to help centre the screws.
I reckoned with washers at the ends it would do the job (but not necessarily aesthetically) and I'd know if it worked well enough to justify working on a prettier solution. With my cobbled up double screen as well, my GP's going to start to look quite eccentric
It turned out not to be too challenging. I used plastic overflow pipe rather than copper pipe (£1.50 for a handfull of metres) and to be honest it doesn't look as bad as I'd feared.
I do have some "previous" with mirror mods http://www.zen113982.zen.co.uk/mysite/mods.html#mirror and the problem is usually vibration and blurring. The GP's new mounts seem perfectly rigid, they definitely work - a significant improvement in my rearward view. No vibration or blurring at all - I reckon that the skewed screws might be providing some kind of torsion that aids rigidity. I'm so pleased that I might seek out even longer screws. I reckon another inch would be enought for total rearward vision. Only once so far have I "lost" a gap because of the mirrors - extendending them further might increase that but for the sake of a couple of quid (and easy reversion anyway) I'll probably give it a go.
