I'm a very simple fisherman and don't like a lot of gadgets, and growing up I always used a rope with a rock tied in the end as an anchor in canoes so that's what I did when I started float tubing. I haven't been tubing long but I quickly learned that wind can be one of the float tuber's biggest enemies, and doing what I describe here can turn the wind into your friend.
I run the anchor line up through one of the D rings behind me on my left hand side of the tube, then along the pocket through a D ring near the front of the pocket and then use the velcro rod holder to hold the line by simply putting it under the velcro twice so I can adjust it easily. (If you're a left-handed caster, rig it on the opposite side.)
The small rock isn't usually enough to hold me still except in a light wind, but by keeping it dragging on the bottom, it keeps you pointed downwind with the wind coming slightly over your left shoulder. You won't have to paddle to keep yourself pointed where you want, and the dragging rock will keep you moving slowly downwind so you can work the water fully. Your backcast will be kept away from the back of your head naturally by the wind.
If you used an anchor with this technique I doubt very much it'll allow you to drift, but I use a rock that weighs only a couple of pounds.
My passion for catching fish is eclipsed only by the fish's passion not to be caught.