ya, the results of stim are highly dependent on work capacity/experience. Most people would experience a ton of fatigue from the 5RM squats, so i wouldn't expect there to be any large scale increase among a training group.
For average athletes, they are going to have to struggle off the bat, with squat stim. That's why I liked the IES stuff.
I personally never liked squat-stim, my knees would ache during the post-stim exercise, such as jumps etc. I had some real good jumping sessions when I did heavy squat singles in the morning and jumps at night, but my knees would ache pretty bad.. knees and shins actually.
For the most part, I like approaching stim from that delayed method, ie a workout on monday positively effective what you do on tuesday or wednesday, I think that is by far the most effective way to use those methods. Plus, most athletes, regardless of experience/work capacity, will see results from that. All that needs to be tweaked is what you do on the stim day (exercise intensity/rest intervals etc). Usually the stim sessions are VERY short and to the point, such as just working up to a heavy single, hitting a set on reverse hyper, and getting out of the gym.
pc!