In the dim and distant past I remember that it was possible to fly a JP 3 or 4 (not the 5) with the canopy open
.... ah! Another madeleine moment. Many years ago as a stude I was flying circuits with Ken Tait (RIP - I think in the Flag Bucc), who was a top bloke in every respect.
'Twas a hot day so he decided we would fly a couple of circuits with the canopy open. Cue startled inquiry from ATC:
ATC: C/S .... is your canopy open?
KT: Stand by - we'll check ...
[2 more circuits go by] ..... yes it is!
Edited to add:
Have checked Vol 1 of logbook - think it was in JP4 XP 665 on ....
... 5th August .....1969