No. There is no simple way to do that.
Good.
I really appreciate a fim “no”. 
(not kidding! I can make peace with that fact)
Thank you couet!
Yes there is no “simple” way … using “ChangeLabel” may work but that’s very painful and will work for one given histogram. I would recommend to use that way if, for example, you really need such representation for one specific histogram for some publication in some paper.
My issue is actually related to the width of the tpalette, which also affects the size of the “colored area” (where the data are plotted… I don’t know how to call it. Graph maybe…?) of the entire picture. And labels are cropped because of the squared shape of the picture.
I can’t edit the aspect ratio, nor the dimension and the position (it must stay in the center) of the “colored area”.
I’ve hundreds of pictures that I edit after that root makes them, using a bash script that took me an entire day for setting the right numbers. I’m a bit short in time to re-do the entire thing again.
So, it’s ok the way it is.
May be just move the palette in that case.
I tried that.
I opened a thread here about that, indeed: TPaletteAxis size
When I try to use it in a script I wrote, I get some “Segmentation Error”.
I don’t want to debug it.
I think the thread you mentioned was replied.
I know.
And that example works.
There’s something that doesn’t work when I use the same commands in my script.
I assume that the “DrawCopy” command makes some mess. 
Ok. Post the non-working script if you want some help on it.
Actually it is online: https://github.com/amivaleo/mctalHist/
After compiling the code, launch the script “mesh.sh” and it will draw a picture.
I do not expect you to work on that. It takes way too much time.
