Not being an AAIB expert in these thing but I think JETBLU has a point.
The deris field can not lie.
if the RV was in the climb out and in a left turn then the DA40 would have been covered by his wing. IF he then eneded up lower but climbing and the DA40 on a constaint height and heading the RV pilot would not have seen the DA40 approaching from behind until too late and would ahve hit him from below so the DA40 pilots would not have seen him either.
But if the DA40 had reported X-wind then looking at the standard circuit pattern you wouln't expect it to be over the coast until near the harbour entrace. Odd that the prop landed where it did?
But there I go being a Bar room Expert, which I'm not. Just putting forward one theory which is all it is.