I stacked them together, I didnt gain anymore size or strength than just S4 solo. Nothing dramatic or even noticeable than S4 alone. My theory is its competing for the same receptors.
I got good strength and some size from Osta. When I added S4 didn't get any more strength or size but got endurance and leaner. I think it's a good combo,just takes a while to sort out the S4 dose to minimise vision sides. Liked Osta at 25mg/d
i got a couple weeks left on the S4. i come to the conclusion that its a great bridge if you dont want to juice and still see good result. Has the ability to keep muscle while getting lean!!
in the future i will use it as a bridge or def straight after PCT. i would start the osta during pct as it takes 3 weeks to build up then hit the s4 after pct.