If Meso 1 is Endurance, Meso 2 is Hypertrophy and Meso 3 is Strength, could I conceivably get strength without the size aka "bulk" by just doing Meso 3? (I'm asking from the perspective of a seasoned Cathlete, not a beginner exerciser).
IMO...how much 'bulk' you put on during Meso 3 will depend on your body and also on how heavy you go with your weights. I have done STS twice now and I got noticeable improvements in my strength, definition and some increase in muscle size (which I needed). I loved the results that came from the hard work of Meso 3. With my body I have to work hard to put on muscle and STS is the best way for me to do this. But I have read on the forums that some Cathletes seem to bulk up with STS. Personally I do not worry as it is only a month and once I rotate to other programs of Cathe's the amount of 'bulk' decreases slightly. The gains in strength are so empowering that you may find it is worth it regardless of look on your own body. However, if you are concerned perhaps you could use weight loads that are more conservative rather than pushing yourself to the ultimate max.