Why can't the glider pilot instruct the tuggie where to take them, on the radio? It seems odd to be at the whim of the tug pilot as to which bit of the sky he/she takes you to.
They can, as in "go for the cloud at two o'clock", "head NW" or "drop me over the town at 1,500'" but on a busy frequency a continuous "left a bit more, no, right, stop there, now left a bit..." to follow an energy line through the sky is something best left un-communicated.
A good tuggie will do this without prompting, much like arranging to cross the edge of a thermal with other gliders in such a way that it doesn't conflict with them and allows the towed glider to sample the lift before committing to a release.
Some would argue that using the radio on tow is an unnecessary distraction but IMHO if you can't follow the tug while transmitting a short sentence, you shouldn't be there at all.