Paul, your explanation of what happened today is spot on.
The grip certainly disappeared as soon as it rained, which made judging the jumps a lot more difficult.
Roger actually commented to me on the lack of grip and we put it down to the levels of sand and new astro on the track.
I could only get one type of rear tyre to grip and unfortunately it won't be allowed at the National.
I am sure it will be sunny in June!