Quick question about iM's

I'm mainly asking this due to HS/PE1>iM, but it applies to all iMs. Does it count as mastery if you have to warm up a lot first? I'm aiming for 20 inches between my hands (the width of my shoulders) for PE1. My best so far is 28 inches, but I have to build up to that; when I work on shoulder mobility outside of F1/H1 I do lots of sets of the iM, getting a little further in every time. My first set is typically ~6 inches further out than the last one. If I was at 20 inches instead of 28 after fully priming the shoulders, would that count as mastery if I could then demonstrate it paired with HS/PE1, or should I be able to get the full ROM with only a light warm-up?

You need full ROM for all 5 sets.  It shouldn't require extreme warm-up, but some warm-up is expected and part of the program.  You can even do a few reps of this iM as part of your warmup.  

 

Remember, one point of mastering this iM is to prevent injury on the following iMs.  Whatever warm-up you need to demonstrate mastery of this iM will be needed to warm-up before beginning future iMs like dislocates.

I always do quite an extensive shoulder warm up before doing H1, it makes a big difference.

I agree with Tex, all 5 sets must be mastery.