Not ALL of the FW flavors have to be used at a high percent.I have used there rocky road at 3% which was great full flavored,at the same time,have used vanilla custard starting at 30% for full flavor.If you look at Capella's brand they have it listed as a suggested starting point .25-.50 percent too,but again,not all of there flavors need to be used that high.
EDIT: I would suggest start low,say 3-5%(rocky road is good at 3%)to start with,and add as needed to get the full flavor.I have not made all of my FW flavors yet(i have 21 FW) so i am not sure which are good at a low and high percent.