That lens is definitely hand holdable. I can sort of relate to it as I hand hold my Bigma all the time at 500mm for bird shots with no problems.
However, you may find that for hiking, a monopod may be more trouble then it is worth in its awkwardness. I missed a lot of shots with my Bigma due to set up times with my monopod. A long monopod isn't the easiest thing to travel when hiking either. It was a royal pain, much like a tripod would be.
You may want something like this.
It is called a Bushhawk shoulder mount. You use it exactly as a rifle. With a sling, you can even shoulder that heavy lens for long distances, and have it instantly ready when you need it. It works very well. Some will tell you not as good as a monopod, but I beg to differ.
There are other options out there. You could use a mount used for a video camera. Some of these attach to your chest area for hand free movements. Likewise, you could use a pocket attached to your belt and slip a closed monopod into this for stability much like those flag carriers in marching bands.
If you are curious about the Bushhawk, just google it. Their web site is easy to find, and their service is very good from my experience.
Just a thought.