The other night a friend of mine and me were working on the 50/50 and talking about the straight ankle lock from there ... If i remember correctly and i may be wrong ( have to double check ) Ryan Hall in his 50/50 dvd said u cant really finish the straight ankle lock from the 50/50 but i get it all the time .. Ive gotten really good with the straight ankle locks because i dont like heel hooking my training partners and the 50/50 is one of my fav positions and hit the straight ankle lock all the time ... So yea most def its awesome from the 50/50 and advise to drill it hard ... The way i do it is a mixture of Reilly Bodycomb's sawing off the foot toes bent deep in the arm pit motion and Aoki's kimura grip deep on the achilles like how be broke Kawajiri's foot... those two combined in one move will most likely get u the tap just dont go too deep on the ankle on your training partners cause u can break the foot or damage tendons pretty easy