I have played with them and will only use it on my top set. Trying to use it less than one a week. I like it when I am mentally not into it or excessively tired. FYI I will use it for up to reps of 5.
Are you training to compete? Level of psychological arousal can affect the rate of perceived exertion, and thus the effective amount of fatigue generated.
Thus, if you are just training to get stronger, I wouldn’t introduce the stimulant into my RPE training variables.
However, if you are training to compete, and intend to compete with it, it may be valuable to introduce it into your training for the purpose of training specificity.
If this line of reasoning works for you, and you use BBM programming, I’d use it for the singles @8 during your peaking phase, and depending on results, possibly adjust for how it may affect your RPE for those singles when chose your back-off sets working weights based off of those singles.