I agree with Fitter2 and others in that T31's should not have been looped,they are 'Normal Category' gliders.The T21 was classified as semi aerobatic and as previously mentioned - it was the fun glider.
I know this is from a slightly more recent BGA publication but it is exactly as I remember the cockpit placard.
BGA glider data sheet - T.31 (Tandem Tutor, Kirby Cadet Mk III)
