I decided to do this one to make it easier for people to select a muscle size when commissioning but also to show what the max size is I feel comfortable with drawing. Anything too much bigger than 8 overstretches anatomy too much for me to really do it well, especially when you want to "pose" it still. So if you want much bigger than that I am the wrong person to ask.

Anyway I hope this helps ^..^

Here's a link to a larger version:
https://www.dropbox.com/s/xv30973xpw7ok3p/mucle-size-ref5.png?dl=0

PS: You can feel free to use this ref for your own purposes as well