wsmalley,

Basically a way of creating a more powerful, more aerodynamically balanced, and easier to mass balance, control surface. Gives higher effect while reducing force needed to actuate. Similar to a stabilator horizontal tail, but of course at the cost of more drag. Also vulnerable to airframe icing, a concern for full scale. Will work fine on models. Don’t get the hinge line to far rearward. You want to retain at least some positive feedback. You still see these on some experimental aircraft. The surface attached to the elevator of the storch is a boost tab of sorts. You see smaller versions of this on modern stunt planes to reduce actuation forces. Hope that helps.

Multiflyer