This may not be true....but I've heard that the Yankee could go into an unrecoverable spin because the fuel tanks were not properly baffled. If the plane started to spin the fuel would slosh towards the wingtips, sometimes increasing the centrifugal force beyond what the rudder could correct.
A friend who instructed on these in the early 70s said they spun them all the time and were recoverable as long as the tanks were full for the same reason you mentioned.
Break out pen and paper and write away! When they changed the airfoil to make the plane 'more' stable, Dicey Miller told them they ruined a perfectly good airplane.
I got a little time in this bird. They are a bit underpowered and unforgiving. Diversions from the envelope can be a little abrupt. Cruises real quick on that little powerplant, though. Jim Bede loved blind rivets and this bird is full of them. No bueno.
