$300 homebrew wing levelling system

With the summer thermals upon us, and not being able to scratch my nose
without having my small homebuilt tossed off course got me to thinking
about how to build a low cost wing leveller.

A small servo tab mounted out on the aileron, controlled by a jumbo
sized R/C servo would probably work fine. If the tab was sized fairly
small, even if the servo went nuts, the pilot could easily overpower
it.

The servo would be controlled by a rate gyro that is also used in model
airplanes and helicopters to provide the stabilizing function.

The overall system would be controlled by a simple pulse-width
modulator using a 555 chip. A small amount of trim adjustment would be
provided.

Operation would be simple: turn on the system and adjust the pulse
width trim knob to get the wings level. Sit back and scratch your
nose, take a pee, eat a sandwich.

This simple system could be put together for under $300. Any thoughts
on how it might work?

tom