Not that I want to sound like a spotter, but what I was trying to say was that it was only the 5s used for pilot training which had the strakes. The 5a wa the new Nav kit mod, but the 5a was used for pilot training and the 5 for nav training. The 5as which were subsequently used for nav training and which had tip tanks fitted and strakes removed were designated 5bs.
WRT B/A ratios, I only flew the 3 at CFS. Can anyone remeber any limitations about spinning with tip tank fuel?