The recommended dosage of ostarine is 25mg/day. I would run the S4 at 50mg/day and ostarine at 25mg/day for 8-16 weeks.
After the SARMS cycle, run a bottle of a good natural testosterone booster like HCGenerate ES from n2bm.com as a mini PCT. 5 capsules/day for 30 days. After the mini PCT you are safe to do another cycle of SARMS.