You can't really have a size diff throuple cause one of them has to be medium

@dragon but have you considered:

size diff couple with Big, Small, and then Wide

if big is 6"2' then wide is 6"6 across but only 4'2' tall

@bees wide is brilliant. You gotta bring more dimensions into it!!!
@dragon we have 3 dimensional axes, which means that we have 8 unique sizes for size gap relationships.... the power of math