[mark yundt]

This is the same problem I run into with full size statues,,unsupported arms. It might seem silly to some until you try carving for several hours with your arms held horizontal,,with a mallet in one.Gravity is a great equalizer!We not only have to support the work,,but ourselves as well.
For a few minutes here and there it's not an issue. But comfort for the long haul really is. That was the point of my mallet,,locking in work,,access to tools.Making one odd move just once is inconsequential,,do the same move a few hundred times and it becomes really tiring!
To get these little trees done ( the big one left on Fri. AM) I carved 12 hrs straight on Sat..and 14 on Sun.If all my "soldiers" weren't in line,,I couldn't do that. Mental fatigue gets me before physical fatigue or I could have kept going.
Seeing how you did the sign,,you were able to lean on the piece and support your weight and arms. Sure ,it gets tiring leaning over,but with the right height seat,,and possibly tipping the piece slightly ,,like a drafting board,,you can still rest ,,and carve more comfortably by leaning on it. Get yourself up closer to the piece,,you need to be able to adjust the angles,,if your sitting the lower edge might even be in your lap touching your belly depending on the angles you use.However you do it,,you need to have at least your hands,,the outer edge,or heal of your hands supported.Even doing the clay reliefs,,I made a board that bridged the piece so I could basically rest my hands and arms on it while I worked. It was just like the sticks painters use for stability to reach the center of a painting. All these little things add up quickly to provide steadyness,,accuracy and comfort .
I'm not there,,but it appears to me that your device is holding the piece at too steep an angle from my experience.Tilting it back,,getting it in closer ( so you don't have to hold your arms out in mid air) so you can pull your arms in closer to your body ( more powerful) and possibly adjusting your seat ( I have 5 stools in my shop,,all different heights) and you should be able to make this work out fine,,so you don't have to work as hard.

[Hi_Ho_Sliver]

What if you made a fold out attachment to the side that you could put your forearms or elbows on....on an upright in the dog holes on your bench to do the same? just a thought!

[Just Carving]

Before we switched over to CAD at work, I drew mostly everything in ink on mylar. Even when I worked with pencil on paper, I still needed to be careful where I put my elbows and forearms--otherwise the linework would get smeared. It is tiring when you constantly need to keep your arms away from the work--or in the carver's case keep them in the same position while holding a tool(s). It is also a problem healthwise--eventually it could lead to a repetitive stress injury which results in muscle soreness, cramps, fatigues, muscle strains, etc. As much as it isn't a cure-all, I do have a solution that helps somewhat whether it be with drafting, carving, or even work around the house where I need to keep my arms elevated, e.g. painting a ceiling. The solution is working for short periods of time. Take breaks often. I use this especially when working at a computer all day. Keeping your arms and hands in the same position for a long period of time causes a strain on the muscles and joints. So, stop every half hour at least--probably better every 20 minutes or so when you doing something like carving. I know it doesn't help when you're on a roll, or if you're trying to meet a deadline, but it will ease the aches and soreness, and in the long run, it's better for your health.