So, just one thing is missing...Personally, I have found that convexing a stone does improve speed. I have two "Special" grade Ardennes Coticules, one from Jarrod, and one from another vendor. The stone from Jarrod is convexed by him and clearly cuts faster than the other which is flat. Other than that the stones feel and behave very similarly.
I also have a soft La Grise coticule which was pretty useless until I decided to convex it myself. I mean really, it was a total dud. Since putting a convex surface on it the stone has sped up enough to be very effective. I have run full progressions with the stone including bevel set right through to finish. The stone just wouldn't handle that beforehand.
If I had one I'd send it to you.Does anyone have the means to put a hard Swedish steel Tanifuji on a convex ark for science?
Alas, I do not have one.