Hi Skyraider,
Sorry I don't have any positive reply for you. The source of your information about CA 15 - P51D trials would be useful to get onto the right trail. The 2 main references I have Wirraway, Boomerang and CA-15 in Australian Service (Stewart Wilson) and Wings of Fame Nbr 4 do not mention such trials. The first reference does have comparitive performance values for the CA 15 against P51-D-5 and P51-H but I suspect that these are just specification comparisons (and there would never have been any P51-H's in Australia). Flight reports from CAC for all the 23 flights there are included in Ref 1 and these are shakeout/calibration flights - no mention of trials. Similarly Ref 2 describes calibration flights after handover to the RAAF but once again no mention of P51 trials. There are some photos of P51's (Actually CA 17) Mustangs in the background of the CA-15 but these are likely to just be aircraft waiting testing before delivery. You may want to try the ADF serial website - they might be able to give you some leads -
www.adf-serials.com
Just for information, if you are planning a painting, there is an air to air photo of the CA-15 taken directly from behind the rear turret of a Avro (GAF) Lincoln so that might make an interesting formation picture.
Cheers
Michael