Re-fueling.
I believe it is possible to use the Ducati Mathesis Tester (not sure if I spelt that correct) to richen the mixture - maybe not as refined as a power comander but almost as effective and a lot cheaper.
There are some great links from the Sigma site to some Australian and US sites with 620 set-up graphs etc., (also a load of techie stuff on relative pros and cons of the 620 and big bore 600 motors).
Air box top mod and cans liberates about 4 bhp and makes little change to the fueling; hence the Mathesis trick.
Re- minin Twins.
TP is right, the BEMSEE regs would now permit an 800ie - trouble is I have a feeling it might break the 72bhp limit with standard cans!! Not sure if N. Glos' have also amended their regs.
By the way TP - well done at the weekend, brill results especially for a 1st time out.