Where the needle valve contacts the float tab, is there a dimple? If there is, file the tab 'til the dimple's gone or fill the dimple with solder and file smooth. Then see if it leaks.
I think you nailed it, all 4 tabs had a good dimple where the needle touched. The ones in my spare carbs had almost no dimple, I filed them smooth and polished them with my dremel. I've tested twice and no leaks so far, just have to adjust #1,3's levels a touch and re test a couple more to be sure. So far it looks like the problem.
Thanks everyone for all the advice, much appreciated! Always good to have other peoples ideas, when crossing things off the to check list
Edit: problem fixed, I even swapped to og floats back in after filing off the dimple. #3 is now holding a nice stable fuel level as the rest of them. Real happy, now tuning for the new airbox setup. Thanks again for the help.