I never did cardio more then 2x a week with STS. Anyway, I think KidMax and PuppyMax is more then sufficient.
i did this (cut back on cardio) in the beginning when i first started STS and found that i didn't stay as lean as i liked. Even though it was hard, my body type is such that it needs more cardio. I've tried to compensate by lowering my cals instead of doing cardio but that doesn't work for me; it just makes me too hungry since i'm only eating 1500 anyway. So for me, i just had to accept that i had to do more cardio and thats what i have been doing and i'm really loving my results. Currently i do cardio coach or a kickbox workout on tuesday, thursday, and saturday, and then on monday, wednesday , and friday after my STS workouts i tag on 30 minutes of steady state cardio either on the treadmill or elliptical. It was hard at first but once i decided this was what i was going to do and it became part of my routine my body adjusted.
I kept up with cardio but felt VERY fatigued, especially during Meso 1. I do believe though that a lot of it had to do with not getting enough sleep. I routinely make do with 5.5-6.25 hours of sleep and honestly, to make it, you probably need at least 8. If you can find a way to bump up your sleep, but not cut out your cardio, I think you'll find yourself with plenty of energy (and fabulous results.)
On Meso One I had alot of energy and my endurance for cardio I noticed improved greatly. I was doing 5 to 6 days of cardio every week. I'm on the 6 month STS rotation so I was of course on Meso one for 8 weeks. I'm now on my second week of Meso 2 and I feel really wiped after my weight workouts and have pretty much kept it to 3x a week and occasionally squeezing in 4 X's a week if I can handle it. I wonder how I will feel when I get to Meso 3?