It's a bit of a myth that the wide chord rudder was fitted to aid spin recovery. It's true there were a number of spinning accidents to the type on introduction, but the fix for this was the anti spin strakes and a change in the recovery technique. The wide chord rudder was principly fitted to give more rudder authority for aerobatics.
The myth is perpertrated by the fact that in the UK, spins are prohibited without the strakes and the new rudder. A mate owns a Chipmunk in Australia where no such restriction exists and spins his. He says there seems to be no difference between those which have both mods and those which don't.