can't remember the thread it was in, but sauerkraut posted up the math on 750cc @43psi vs the stock injectors at 58psi. it gave the % difference between them, then you just start out by pulling that %. do a search on sk name and you should be able to find it.
I don't remember what post that was either, but the 650's on stock pressure flow around 750cc. the stockers only flow 577, So they will only flow approx.77% of what the 650's do. Inversely, the 650's will flow 23% more than the stockers. To even out your fuel trims you should be pulling about 20% in the low throttle settings. Get a scan tool or logger and start by pulling 15% and work from there.