poor lateral control on a slow tow?

As an aerodynamicist/flight dynamicist recently re-soloed after 25 years
off, people keep asking me hard questions. One that has come up recently is
why a heavy glider on tow feels horrible, but thermalling in the same glider
at lower speeds is fine? (see also Mike Fox's article on aerotowing in the
October issue of S&G).

I did some calculations, and I reckon it's probably due to the tug wing wake
(tip vortices generating a downwash inboard, upwash outboard) changing the
lift distribution on the glider wing - with an increased angle of attack out
at the tips reducing aileron effectiveness. There's possibly an interesting
academic research project here, but it's always best to get a reality check
first ...

Is poor handling at low speed on tow a common experience? I'd appreciate
any thoughts/comments/war stories ... particularly bad tug/glider/speed
combinations, incidents of wing drop during a tow etc etc?

Doug Greenwell