So here we go. 65.80 and 61.44 in practice. With timed runs of 60.98 and 59.06. So, job done. And, after driving home again without incident, decided not to race on Sunday and keep it safe for next weekend's trip. Instead I could get on with the frontend.
The trip had confirmed the need to sort the frontend damping. Fortunately the car now seemed to be avoiding the rear bumpstops in an any too-obvious way. But the front left corner was under-controlled and too much weight being transferred onto the right rear corner.
And thanks to John Crae for his omnipresent photographic coverage - https://jcrae.smugmug.com/