I am (or "have") transitioned to one-sticking this year.
I've set myself a couple of goals:
1. No active mechanical aids for either climbing or rappelling, but a passive aid like a figure 8 is fine.
2. Once I tie into my bridge carabiner, I don't unlock it until I'm back on the ground.
3. I've always got a tether with minimal slack to take my full body weight.
4. A little bit of slack in the tether line is ok; maybe 6-12", but not several feet.
Here's what I've come up with: I'd love comments/critique. You ain't gonna hurt my feelings; I'm going for a balance between usability and safety, so please lay it on.
* I'm running 8mm resctech and using my rappel line as my tether, with a friction hitch connecting me to the bridge: right now trying to make the cosmo hitch work, but I may go back to the Michoacan plus a munter hitch through the carabiner. I've got a shockcord prusik and a plastic carabiner connected to the tether line to keep it taught as I advance. This isn't weight-bearing, it just keeps some tension in the line to keep the tether from falling down the trunk as I advance and take weight off the tether.
* I'm using an oplux LB with a friction hitch (5-loop Michoacan)
* I'm carrying a second oplux LB/tether with a prusik for going around branches.
* I've got a dyneema sling that I clip into my LB loops (with two carabiners, one on either end) as a second bridge that I clip into my secondary tether (with a third carabiner on the prusik when I need to.
I try to push my tether as high as I can on each movement. As I climb, I'm using my LB but also tending the tether to choke up on it while I'm on the aider, until I get onto the bottom step of my stick. Then, I choke up my LB and put a small amount of slack in the tether and advance it up the trunk of the tree, repeating until I've got it up pretty high. Eventually, I get onto the top step and push the tether up as high as I can; then I come back down onto the lower step and put my weight onto the tether, loosen the LB, and move the stick up. Lather, rinse, repeat until I'm at hunting height. Yeah, I sacrifice a little bit of height on each movement, but in doing so, I keep less slack in the tether line.
If I need to go around a branch or something, I use the second tether rope and clip it into the second bridge, move the main rappel line/tether and then disconnect the second one. Occasionally, for branches that are large enough, I just use my LB for this (e.g., going around a fork where the LB is obviously going to catch in the crotch and it's big enough to hold my weight). The rule here is that there's always something with only a few inches of slack (if that) that can take my weight that's actually anchoring me into the tree.
At height, I tie a bite of rope through an LB loop with an overhand knot or figure 8 or something in case the friction hitch slips.
When I'm ready to come down, I lower my bow with my rope retrieval line, tie in with the LB, choke that up, take the dyneema sling with it's two carabiners and hook that into my bridge, then give myself just enough slack in my tether to grab a bite of rope and feed that through a figure-8. I clip that the other end of the sling. Now, I've got a figure-8 a bit above my friction hitch, then a munter on my carabiner; I remove the stopper knot I put in the rappel line and toss it down. I put a bit of weight on, attach my rope retrieval line to my rappel line, put some small amount of weight on the tether just to make sure it doesn't slip down, disconnect the shock-cord prussic on the tether, and start rappelling down. I stop to grab my stick on the way, but otherwise, that's it. The munter, figure 8, and tended friction hitch mean I come down pretty slowly, but I'm okay with that.
Note that my main rappel line is connected to my bridge carabiner from the time I leave the ground until I'm back down. I don't open it for anything; even putting my back-band on I just unthread it from the triglide it's on and feed it through the (closed) carabiner.
Once I'm down, I disconnect everything, take the hitch off of the rappel line, and retrieve the rappel rope. I tie everything back on from the ground as I'm packing up.
The more I practice the faster I'm getting at this, and I think I'm hitting all of my wickets.