im sorry mark i have no experience with the polini. all you can do is follow what i said
get main jet right then see how it runs at 3/4 7/8ths throttle and to get that right you might be lucky and find the current needle just needs clipping right - like bairdco says.
ive never been that lucky and just gone straight to needle tip. but im taking phbg might not be the same for polini so apologise if ive led you down the wrong path.
main jet -wot
needle tip 3/4-7/8ths throttle
pilot jet idle to 1/8ths throttle
and finally clip needle or taper to get mid range
there will be much better men than me who tune differently (correctly) but since i started doing it that way its become simple for me to get it running well.
to get it running better than just well for me i'd need a dyno or af sensor
or someone more experienced stood next to me. (edited)