Yes, it can be done with a few ultra lightweight "accessories."
Over the past few years, I've been trying to come up with an easy and lightweight/portable solution for "exploratory hunting." My "solution" works particularly well with "harness hunting." (aka: tree saddles) I've tried numerous different combinations and equipment over the past few years, and I finally have something that works! ~ It's fast, you don't sweat, and it's very portable/compact. It adds about 1 lb. of weight to the the two sticks. ~ For those interested, I should have a few photos this evening of my setup.....
WARNING: I'm not saying it's safe, or that you should even attempt it. In fact I suggest you don't because climbing sticks were not designed to work like this. That being said, I firmly believe that the climbing stick itself (being metal) is the "weakest part of the link." As with any climbing techniques, you must be extremely careful.
PS: This technique does not involve moving sticks while in the tree. Once there locked on, that's where they stay. Also, there is no crazy reaching, jumping or other crazy maneuvers involved. I've been climbing/hunting this way since last late October. (I'm 48 yrs. old, 210 lbs. & I'm in pretty good shape. (I do run/jog all summer long preparing for hunting season.) To be completely honest, I've become very comfortable climbing this way, and I've never had any issues. (Knock on wood?!?!)
Always wear a safety/linesman belt while climbing.
This gets you to almost 15 ft:
2 muddy sticks (the ones with double steps that open up)
2 Petzl climbing aiders http://www.amazon.com/gp/product/B00388SAFI (Important: These are relatively short 5 ft. aiders.)
2 10mm "runners" http://www.amazon.com/gp/product/B000P3AUGG (connects aider to bottom part of Muddy Stick)
(I loop these 1/2 way through the aider's "hanging loop" & hang them over the bottom foot pegs before "opening them.")
To get a few feet higher, I use these:
Bottom "starter" step: 1 Cranford Industries EZY® Climb Folding Rope Tree Step
Second step: 1 Jim Stepp "Stepp Ladder" step (It makes a decent "starter platform" for setting up the first stick & climbing etrier aka aider.
(I suppose you could even use a second "starter" step if 20 ft. is your goal.)
If a Muddy Stick ever "fails", things will "get ugly." Tree must be relatively straight to avoid aider from kicking out to the side, especially on the first 2 steps of the aider (safety consideration). ALSO: While feet are in the aiders, it's very important to maintain upper body leverage using the foot pegs on the sticks.
It's easiest to climb with lighter boots. I've used my winter ones too, but it is more difficult to get into "the stirrups" of the aiders. Also, a red light is not going to help. Green is OK while ascending/descending in the dark. (aiders have an orange step to help you see where to place boot) The first step on the aider (going down) is the most difficult one. The aiders I chose have a first step that is very short (I don't always use it.) But... When you're "struggling" to get your foot in while descending, it makes things easier. ~ It's actually a little easier going up than down because you have to "thread your foot" into the aider! ~ The good news is, it's impossible for the aider to become disconnected from the sticks, because the "runners" are "locked into place" when the pegs are opened. (as long as nothing is ripped/torn)
When I do a setup, I first go up the tree without bow or backpack. I keep a tether to the pack and pull it up afterwards. And to the pack, I have a "Doyle's retractable hoist which "unreels" as pack is lifted. Once pack is hung, I pull up the bow. ~ It's a "one trip up setup." Also: If I'm leaving the setup in a tree overnight and I know the tree "works well" with the muddy/aider combo, I bring everything up with me, instead of using the hoists. (pack on back, and bow hanging from my hip)
At ground level, I setup the starter step, the second step, and I also loosely place the first muddy stick (connected to the first aider) around the tree as high as I can reach. That way, I only have to climb with one muddy stick hanging from my waist (aider already attached).
PS: Muddy sticks are great for attaching the runners (connecting aider to stick) because of the smooth oval design of the foot peg mounts. (and the fact that they effectively lock the "runners" in)