John Giddy wrote:

Have they done any tests at high altitude airfields ?

How high is high enough? Is a 800 meter paved runway at 1328 m (4354 ft)
altitude high enough? I took off in a Janus last summer there behind an
ultralight. It wasn't 40°C, though.

... regarding your lovely country.

You may spare the flattery, I'm not American. ;-)

We have discussed ultralight tow planes, but the consesus seems to be
that with high temperatures (40 C is not at all uncommon) the high
density altitude will reduce the performance to an unacceptable level.

We've discussed it, too, and all experts said that it wasn't possible.
The experiments showed it was. If you want to know, you must do the
experiments in the conditions which are important to you. No way to know
otherwise.

I have also heard some rumours that the high speed Rotax engines don't
take kindly to the extended full power operation necessary when
towing, and the lifetime is shortened. Can you comment on this please

I've heard all kinds of rumours. No, I can't comment on the lifetime of
Rotaxen, sorry.

Stefan