Ref the BD testing mentioned above..I can confirm they did carry out Spin trials (from Upavon).
However, the more I think about it ..I can't remember if spin whiskers were fitted or not?
I think they did about 3 or 4 aero tow launches and IIRC it did not spin too well...but I think they only had the one crew in the front seat so maybe not the best C of G config.