These are Steve Copsey's pictures copied from his Yahoo Group photo album.
This was his accompanying text explaining how he made the modifications and why:
Well folks, I'm sure you will be enthralled and delighted to know that I solved my front mud-flap problem before my epic first off-road ride last Sun. On Saturday before, armed with a fresh new shiny £7.99 B&Q dustbin, I set to work on a design extravaganza ;)
I figured out that because the header pipe drops so low it would make more sense to make a horizontal lip that fitted over the U rather than under (ie in the gap of the U), so using cereal packet as a template, a small upside-down L-shaped bit of plastic was fashioned, tie-wrapped to the down-tube, with enough space around the up tubes of the U not to melt it.
This then gives a horizontal "lip" which serves two purposes - to reduce the mud going in an upwards direction from the front wheel, and more importantly, to stop the mud-flap bending against the exhaust.
With that in place, the right size for the mud-flap can be determined, extending an inch or so below the lip of the fixed guard. Note that on almost all modern bikes you can't just bolt a flap to the mudguard as it will be angled too steeply back and will rub against the exhaust etc.
So using two vertical mounting points, the lower one needs to be spaced out 10mm or more to push the flap back in towards the wheel, using some chopped up bits of dustbin an inch square with a hole in the centre.
A bit of experimenting is needed - the flap should be close to, but not touching the exhaust, and the "lip" on the fixed piece should just lightly touch the flap so you can't feel it rubbing through the steering. If the flap is not very close to the exhaust it will definitely hit against the tyre at some point!
Use a tie-wrap for the lower and a small bolt for the upper - a small round headed bolt is best with the head on the inside - if the tyre does hit the guard at full compression it will just slide over the bolt head and cable tie and not catch.
Unfortunately I forgot to take a picture as it worked brilliantly on the ride, keeping every drop of mud off the engine. Muddy water goes everywhere unless you go steady, so you have to accept that part however. Will post some pics in next week or so,
Thanks for the other replies - the heat-proof tape is a good idea for a simple design certainly. Mk II coming shortly will be a slightly wider flap, and an aluminium L part, just to look a bit better.