Jetting for Keihin PWK 38mm airstriker on RB

Hi, I've got an RB20 tuned for sprinting and have a Keihin 38mm Airstriker carb that I want to try on it. Do any of you guys use one on a tuned Lambretta set-up as I believe the Keihin carbs are far more popular in mainland Europe than in England. Just need a rough guide, mainly on the needle and I'll work it out from there with plug checks. Cheers, Corrado.