Leading Edge Slats on the Me-109

[Crumpp]

you will stall her of course when you do a mistake and lose control

Again, they act like training wheels on a bicycle. In otherwords, it should be EXTREMELY difficult to spin the aircraft and very easy to recover.

once the a/c enters the spin

The advantage of the slats is in preventing spins. Find a report on the spin characteristics of the Bf-109.

There is an engineering reason there is not one.