Franco-Belges Kiln Coffee Malt

Just found this malt on NB’s website and I’m interested in it’s possibilities for a stout. I’m planning on doing a small test batch of and imperial stout and was thinking of tossing in a bit of this to see how it turns out. Maybe 3-5% of the grist?
Another random question: has anyone used a bit of Special B in a stout of any kind? I don’t have any experience with it but a heavy caramel and raisin flavor sounds possible good as well in small amounts.

I use a bit of it whenever I brew a coffee porter or stout; should go good in an imperial stout.