Congrats on all the improvements you're observing. One thing I noticed between the two STS series is progressive overload is built into STS1 as a constant reminder to increase your weight load over time. STS2 has Cathe verbally remind us to increase the load every once in awhile. So when doing a STS2 rotation I found it helpful to add in a week of Xtrain Burn Sets for UB every 4-6 weeks just to push myself to failure on major UB lifts as another gauge for increasing the load. Many trainers recommend a AMRAP day for your major lifts to gauge progress also. Since you are about to embark on that Body Building Rotation, you might consider using some specific workout(s) to use as a gauge on your progress. Of course if you are really diligent about progressive overload you may not have any need. It's just a thought.
Good thought - One way I make sure I keep up with progressive loading is when I'm marking down my weights that I used in a workout. If I'm finding I feel like I could go heavier the next time I do the workout, I add a + next to my written weight selection, and the next time I do the workout, I go up an increment based on how many +'s I put next to my weight notes.
If the goal is to do 10 reps and I only managed 8 or fewer, I stick with the same weight for the following week until I can get the full 10 reps, then increase from there after.
I do think it's going to be a bit of a challenge really gauging my strength in the next few months because that Body Building rotation doesn't have a lot of repeat workouts. All I can really do is reference my 1RM notes from when I finished up STS and then calculate if I'm going to push for 75%-80% of my 1RM with listed exercises in the workouts. I've been prepping my workouts beforehand that way instead of just going by "feel".
It's a bit of a gamble when she throws in completely new exercises - like those Pendlay rows. They're not in her WM/1RM calculator - I had to take my best guess at what I could maybe do based on my traditional barbell row notes - just go a bit lighter because the Pendlay position is more intense/advanced. I did go heavier with the Pendaly rows than I have in the past with some confidence knowing I'd gained strength after doing STS, but even then my guess was wrong because I definitely still could have gone heavier and matched Cathe's selection.
Maybe after finishing the second week of STS 2 Body Parts workouts next week, I could go back in and re-calculate my 1RMs from there, and since I'm keeping everything on a spreadsheet, I can add the Pendlay rows (and any other different exercises).
I suppose this is good argument for doing STS a couple times a year if you're following a specific series - keeps calculating and upping your 1RM % at the top of your mind.
Though I'm still noodling around with the idea of using STS 2.0 to replace STS at the end of the year - which will definitely mean some more diligent note-taking and re-referencing my 1RM notes - and also truly planning each week to increase the %.
If anyone's read all of this congrats - I find I use these posts as a spot to reason things out. Like honestly, this post has taken me an hour to write as I go back through and think of what I'm planning.
I think it's an accomplishment to fully complete the series as designed. 
