Line spacing at the handle results in total throw of the control surface in exactly the same way that servo arm length at the servo results in total throw at the control surface of an RC airplane.

If the model is too sensitive you can simply adjust to closer spacing at the handle. Even the old iconic handle included with just about every Cox airplane ever sold I just measured 3.5 inchs widest (most sensitive) and 1.5 inchs closet (least sensitive). I also just checked an old Carl Goldberg Half A handle and it too is 3.5 inchs at its widest but only three quarter inch at its least sensitive adjustment.

I believe half A bellcranks in most cases do just fine when a half A handle is used and set up or adjusted properly. A four inch only handle is of course going to be perhaps overly twitchy.

John