Hi there BLRKATZ. Welcome to the forum.
So much great info and support to be found here! For example, here is a thread on the topic of shorter time to implement STS. Some great options are noted, which, with streaming, you may be interested in:
http://cathe.com/forum/threads/a-shorter-version-of-sts.303351/#post-2343101
I think STS can be modified to fit into 45 min. Of course you won't get the exact same results as you would if you did the full program, but I think you will still see some great results and will enjoy this awesome and challenging program. Life is not always perfect. We all have to do what we can do!
-Meso 1's upper body workouts are set up as supersets or tri-sets and so you could do a couple less sets than Cathe. She does 8-12 sets but you could do 6-10 sets. For example Cathe alternates between back and tricep exercises 10 times on disks 2, 8 and 11. You could follow along with the program but skip over the last 2 times she does back and triceps, completing 8 supersets instead of 10.
-Meso 1's leg workouts all have some optional leg moves at the end of each program. These are the moves which require no weights. You could omit those and skip ahead to the stretch.
-Meso 2's upper body programs are a little trickier to modify as you will want to keep the integrity of the double wave structure, sets with declining number of reps, going to failure, etc. Because Cathe works one body part at a time you could do one less body part on those time-tight days and do the remaining part of the workout the next day (e.g. work back on one day and biceps the next day).
-Meso 2's leg programs are all close to 45 min. so you may be able to squeeze them all in. If not, you could do each tri-set 2 times instead of 3 times through.
-Meso 3's programs are laid out with 4 sets of the same exercise. You could do 3 sets of each exercise. This way you do all the various exercises and maintain the same rest periods (important), but just wouldn't do the same total volume.
-Meso 3's squat rack routines are all over an hour. However, the plyo leg routines all come in close to 45 min. and so should be a better option for you. If you find the plyo leg routines still a little too long for you, I would omit a couple of the latter cardio moves but do all the strength moves. Given that you are probably doing lots of cardio on your non-STS days, you may be able to get away with 2 minutes less cardio at the end of your 45 min. time frame, while keeping the structure of the workout for the majority of the workout.
In terms of the Total Body workout, I too have wondered when people have worked that into their STS rotation effectively (if used all when doing the 3.5 month rotation).
I have used it during the active recovery weeks (just doing it twice/week).
The program uses lighter weights (60-80% of 1RM) so it worked OK for me, but I am not sure if I should be lifting at all during that week. Any input from other Cathletes would be appreciated.
Hope you will enjoy those precious 45 min. you have to yourself each day!
Jane