Go to our website here http://go-racing.vpweb.co.nz/Tech-Tips.html

Scroll down past the run-in info to the tuning section.
Basically with the longer tapered LSN you just need to make sure the top end is rich enough to allow enough fuel past the LSN at WOT, as with the GX Series the fine tapered end of the LSN remains in the receiver jet even at WOT.
The GXII-5RHO LSN has a modified taper, that allows it to just clear the receiver jet at WOT, so this tuning issue is not quite as sensitive on the new GXII.
The longer LSN gives a smoother power band, as the LSN controls fuel delivery from idle right up to 95% WOT - you have no major transition from the LSN to the HSN to tune around like a normal short needle carb.