My university has upgraded to Moodle 1.6.2 and now everything is much better
In particular, the activity reports, even the complete reports of students who've done dozens of Hot Pots and written lots of messages in forums, too, arrive in just a few seconds. Wonderful =D> (Oh! it doesn't work here. In Eudora it shows hands clapping.)
Since I've realised the students can find the whole list of Hot Pot exos by going to "Hot Potatoes Quizzes" they don't need the whole list in the central "Topics". Just the first exercise in the chain has to be visible. I've realised too that when the chain is added, the topic has to be "visible" to the students. Otherwise when the topic is later made visible, the whole chain is visible and each exercise has to laboriously turned off one by one.
Anyone interested can see the new "look" at L3 - Read English - GREFOPS. The enrolment key is : Rennes
You'll also be able to do all the exercises as a guest. I don't know if this a problem or not. I asked the question a year ago and nobody seemed to think it was, but maybe they hadn't envisaged a course made up entirely of Hot Potatoes exercises.