Length = 545mm (from the gearchange crossover tube to just under the upper front cross tube)
Width (rear) - 265mm (it will need the corner removed on the right side to clear the gearchange crossover linkage)
Width (front) 163mm
I used stainless rubber covered "P" clips to hold it in place. 2 x 22mm for the rear, 2 x 20mm for the front.
I made mine from 3mm aluminium, however I would advise using thinner as it was a bear to bend.

Cheers,
Kamel.