I like yoga as well. If only I did it more.
Listen to your body. If it's too much today, it's too much today. For me, some days my hands are sore, so anything placing my hands on the floor is a potential no go those days. Regarding good vs bad pain, that fine line you'll discover as you go. If it hurts a little the first cycle, hurts more and more with each repetition, liste to that.
36 yo male - USpA mid-2015
Medications: meloxicam (7.5mg daily) and cyclobenzaprine (as needed) in mid-2015; hydroxycholoroquine early 2016; methotrexate 0.6cc Jan 2017 w/1mg folic acid daily; waiting patiently for insurance to approve Enbrel
Supplements: multivitamin and fish oil
Other: allergy shots for 10 years as a kid, and again since about 2009 along with zyrtec, flonase, and montelukast