From testing ive seen that at least on simple difficulty (havent gotten the chance to try regular or expert) the stretch attack is always alternating, so it wont attack the same spot twice. Either that or i got lucky in all my attempts and it just worked out.

I found that standing on either the middle platform or on the far edge of the nearest platform to cagney gives you a very small but noticeable amount of wiggle room to react to whether the attack is going high or low. Other than that i suppose its down to simply training yourself to see what animation its doing and reacting fast to it.