just chiming in to say what worked for me. i found this post when trying to figure how to attach an ebony wood armrest to my guitar.
it came with no tape or instructions or anything but the piece of wood...
i was worried i would need a very strong bond to keep my arm from pulling it away but when i read people here used two sided tape i decided to try the velcro ovals i already had. i got them at walmart. they are sticky backed and i put a bunch of them on covering most of the surface of the armrest, and they work great. three or four would probably have been sufficient (instead of the 8 i used) and i was able to readjust the position when i found the first try was not quite right.
what i found was that you really dont need any super duper adhesion force there. they way your arm will contact the rest doesn't tend to pull it away from the guitar with much force at all. the rest feels solid and im not worried about it coming loose at all.
i cant say what the sticky ovals might do to the finish if you tried to remove them but i doubt they'd be worse than the tape.
also i bought my ebony wood armrest from a seller in india and it looks much like the one mentioned earlier in this thread. it is real ebony and it was much cheaper ...
his store:
https://www.ebay.com/usr/violin-india
the one i bought:
https://www.ebay.com/itm/2-different...e/281857327488
thanks for the info ....