kyllo, you didn't say exactly how long you did SS for, but it's my understanding that gaining even 20lbs of muscle in 6 months is virtually impossible:

"Under the best possible circumstances (perfect diet, training, supplementation, and recovery strategies) the average male body can manufacture between 0.25 and 0.5 pounds of dry muscle tissue per week"[1]

For sure SS will get you stronger in an almost magical fashion (I'm currently doing a modified SS program) but expecting to gain 20lbs of muscle in a short period of time is unrealistic.

[1] http://www.t-nation.com/portal_includes/articles/2006/06-154...