I think winstrol would be prefect for a sust/deca cycle , I call this the "triple threat stack" . Because you have test as a base , the deca and a synergistic anabolic and with the winstrol a 17-AA you will have a combination that will work in harmony.
Winstrol also counter the progestrone side effects of deca so it is recommended that you add it in your cycle.
As for side effects I think if you use deca you will be fine but using winstrol on it's own can give you sore joints and it is harsh on the liver.