I am still learning. I have picked info from a number of sources, books, people, observing and trial and error.
Today I worked a 25' pine log, 6"x7". I do not hew on a regular basis. For times, in line with NH's previous time post, I have 5 hours total in it, it is almost done. I left the last 8' on the end to video, maybe. I noticed that as I progressed around the log the times got longer, I was pooped out. A part of that time was snapping lines and such, a little rest too. I tired four different axes and my one felling axe for a total of 5 axes. Single bevel, double, long handle short handle, I even docked the handle on my newest axe, which I acquired at the geometrics workshop for $35. This new axe is the heaviest but removes the most wood the quickest, it takes it out of me though.
I would really choose the double bevel Gransfors axe as a favorite, but the stock handle is not in alignment with the blade, it bends slightly into the work making it nearly unusable. I shaved the handle down thinner a while back but it's just not enough. I fall back on my home made axe, a kent style which I reshaped, but I think it has too much scoop in the blade, but is really not too bad. It is nice and light. If I was to hew on a regular basis I would rehandle the Gransfors axe. A long handled and short handle version would do all I would need.
I also tired the blubber axe, as Jack Sobon called it I asked his opinion at the geo workshop. I posted a picture a while back some where here on the forum. I would say it could have been used for finishing timber, it leaves a flat surface, no scoops. It still leaves me wondering.
I have not tried hewing at an elevated height. There are a number of methods and combinations from axe type to styles of hewing all with variations.