This should explain the general tendency for an aggressive spin entry from a skidding turn:
http://apstraining.com/traffic-pattern-stalls/
Especially refer Diagram C which is from Rich Stowell.
If you redraw Diagram C in a steady, straight slip you should see why the general tendency for it to be spin resistant.
I've been training instructors in these exercises over the last 15 years or so, mostly in a Decathlon and some in a Cessna Aerobat. Managed to catch a lot of trainee instructors unaware of the approaching stall/spin as the usual symptoms of an approaching stall are not present (or at least nowhere near as obvious as the common straight stall) in a skidded turn stall.
I regard Rich Stowell's book as the best on this subject:
http://www.richstowell.com/shop/book...pin-awareness/
Thoroughly recommended.