Pilot jet size. 34mm Mikuni.

Hi People. I have a stock `69 F/B running a 34 mm Mikuni. I am having trouble settling on correct pilot jet size. I started with#35-too lean. Whacked a #40 in. runs good at 1/2 turn out. Stuck a #45 in and still good at 1/2 turn out. Screwed the mixture screw out 1 and1/2 turns out and backfiring. My question -has any one tried a #50 pilot jet? Should i worry if it runs and starts OK? Leave it at #45? I had a look at Panic`s book and it recommended #25!! Must be a typo. #35 took forever to reach from cold the stage when it would idle fast enough to not conk out. Thoughts? Don`t tell me about Amals. I know all about`em. If i could rubber mount them, i would fit them. Cheers.