and no offense taken, Sorry to hear that you do not even fit in the cockpit, thats a bit rough. For information I did the AOPA Aerobatic Flight Certificate Course, which is a little more than a few spins
I have no idea how much room is in the Extra, the Slingsby and I were a very tight fit although i don't think I had any problem with the canopy although I can relate to the stick hitting you leg as I had that happen once or twice.
Oh well I always wanted to have a go in and Extra, they have a bit more poke than a Slingsby (it's only 100bhp)