I use it regularly with my POTS patients. I like to think of it as if someone was sympathetically upregulated. From an orthostatic standpoint make sure to do initial needling sessions laying down to avoid any vagal, parasympathetic response. You may also consider more superficial needles and starting with a lighter initial dosage until you get a feel for their response to needling.
In addition to treating the pain complaint I may add in needling areas in the upper cervical spine, trigeminal n. distribution, and thoracic (through the levels of the sympathetic chain ganglia T1-L2). I also recently have noticed myself focusing more on the TL junction area in this population. Perhaps the guarding is a function of the psoas origin, diaphragm attachment, location of the kidneys and adrenal glands, or location of the cysterna chyli anteriorly. In any case I often notice significant muscle tone in this area.
Let us know how it goes!