Hi Jon: I've used a monopod quite often, and it is not anywhere near as stable as a tripod, of course, but better than free-holding in most cases (and much lighter and easier for transportation).
But I've seen people using "skimpy" tripods that wavered in a light breeze, and they should have had a monopod !!.
The trick with any monopod use is making it the "third leg" - your two legs are splayed, plus the monopod is out front, and pulled towards you to make the "tri". With a WL finder, though, you have to be careful not to let your breathing and rib cage cause movement (movement which is less pronounced at head level). The WL finder is the issue, here.
My advice (if you had asked) would be to fill a large sports sock with two pounds (kg) of dry white beans and support your HB on the bean bag on any stable surface - car, chair, fencepost, etc, and use a long cable release. (And if you get lost in the wilderness, you can eat the beans and put the sock on your head. <grin>
Colin