BPF,
Thanks for your prompt reply. I'll try your runup procedure on Sunday and report back.
We keep a very close eye on CHTs, seeing as how we spend several minutes climbing at full power and then descending at low power for a similar time. Having an EDM is essential for managing the engine, particularly the "rate of cooling" mode used during descent.
On hot days in the summer, we often have to speed up the tow to maintain the CHT within limits. Luckily all modern gliders can tolerate quite high towing speeds, but the drawback is that the rate of climb is reduced.