Note that the contrast of gestural scores for the [r] part in tr-i and ch-i is clear, because the [r] in /i/ environment shows both TT backward and TB retraction; whereas in ch-i, TT was always in forward position and TB always in rest position.
the contrast of in tr-u and ch-u is more opaque because the TT and TB for both trand chwords are eventually attaining the same position.