I would agree with that, I have a 14 mm and it ends up being a little thicker than an Emporer pen, anyone had one of those will know it's a chunky pen.
TBH I used the 14's once as a commission job and never used them since 
I don't see that a 13 mm pen would be that much different of 0.5 mm thickness. 
If it was me I would go with 10s and 12s Phil.
Or even look at smaller than 10s then I may be interested..:wink: