Originally Posted by
Metaluna
In practice I find I never actually need to use the trim position on my bike, but it's probably a function of things like chainstay length and the specific gear ratios involved.
Yes indeed, it is a function of chainstay length. The shorter the stays, the larger the chain angles get, and the larger the chain displacement at the FD level between largest and smallest rear cog. The FD cage shape is also important: wider = more tolerant but also less responsive in front shifts. Overall tolerances are quite small.