Constant FINS_WITHOUT_INTERFERENCE 

pub const FINS_WITHOUT_INTERFERENCE: u32 = 4;

The most fins that one station can hold before the fin–fin interference factor drops below 1: four (Niskanen 2009 table 3.3, hpr_aero::fins::fin_count_factor). Fin sets at one station with more than this between them are counted apart by hpr and together by OpenRocket (issue #325).