our runways are bumpy and sometimes have long grass (when they havn't been cut) so I guess bigger diameters are out then. I get the best results with a 12x6 on a 53 irvine in an Xtreme Lite, finer pitches just don't work as well so I am hoping the same thing applies to the Synergy. I guess going to a 16x7 may be the best option then. 16x6 may get the revs too high with a genisys mini pipe.