Dear mr. Dowson 
I'm writing just to give a satisfaction to you about my experiences using the "Key tug heading" and "Key tug speed" commands on FSUIPC. Well, the experience leads to nothing.  :lol: I tested lot of parameters on both cases, negative ones, big one, fractional ones, but the only thing the plane did was turn the tail to the right when I requested a tug heading command. The tug speed did nothing at all, but it seems that it made the key tug heading command to stop act on a flight session. Default command SHIFT+P (+1) (+2) were not afected tough. Well, to end, I found no usefull aplications for that on the FS2002. Maybe someone try on the 2004 and find better results. 
Regards! 
Germano Cavalcanti.