I finished my first HST a few months ago, gained ~17lbs, most of that solid muscle. It was great, a lot of people thought I was juicing. Took that as a complement. I did 2 weeks of 15's 4 weeks of 10's and 3 weeks of 5's. I took a layoff for 3 weeks, doing another HST- started today.
Also while on HST, my strength went up through the roof. Bench went up 45#, squat up 65#, deadlift went up 35#.