First time I tried STS I gained alot of weight fast and looked and felt horrible-lost my ab definition, belly got bigger, pants were way too tight,etc. I quit the rotation after 3 weeks and worked hard for 2 months to get back to "normal".
Fast forward several months and I am in the last 2 weeks of Meso 1 for the 5.5/6.5 month rotation. I may have gained a few pounds but I feel/look great! My body is responding beautifully. My clothes all still fit-legs might be a little tighter in my pants but I am okay with it, my abs are defined, my belly is flat, my legs are starting to get some definition in them that they never had before and my upper body muscles are popping!
This being said the few pounds on the scale are not bothering me like they did the first time.
The first time I did this I was lifting way too heavy. I did my 1RM's and apparently did them WRONG so I was killing myself to lift the weights that the w/o card was telling me I should be able to lift for each exercise. I also wasn't doing enough cardio for my body.
This time I've set up the rotation in such a way that I am able to do more cardio. I dropped the weight loads considerably to a comfortable but challenging lift and am able to increase often by a pound or 2 and I am thrilled! I must add here that I did not redo my 1RM's. When I started STS for the second time I picked weights I thought would work and adjusted from there. I love the longer rotation because it gives you a second chance to find that perfect weight! This being said I may not be on target with doing the exact percentages of my 1 rep max but I don't care. I am enjoying the work outs and the results! It's awesome!
I guess after all of that babble, my point is, if your clothes fit and you are happy with how you look and feel, then pay no attn to the scale. If you can see/feel the weight gain and are not happy with it, then add more cardio, lighten the weights...do whatever you think you need to do to stop the cycle and start a new one that works for you. It's not worth it IMO if you are not happy with the results you are getting but don't let the scale alone make that decision for you.