I have a Nova Rossi RX21R1WC, thru like 1/2 gallon only......with 20% fuel, however, I still don't know do I have to add shim under the head........?
The one under the head right now is the SILVER stock one, I believe it is a 0.3mm shim.......for 20%, do I have to add a 0.1mm or 0.2mm to 0.50mm?

I have seen a lot of setup (from serpent) by using 25% and their shim setup are 0.6mm to 0.65mm........and 30% are up to 0.7mm.....

I am only using 20% now.....do I need to add shim? or setup to 0.5mm total? Thanks.......