Has anyone used mahlab in beer? How much? When did you add it?
Not mahlab but other stonefruit pits. Cascade Brewing (rip?) made a sour beer with other stonefruit pits which gave me the idea to do the same. Add as a secondary addition.
Depending on the beer, you may need to add a hefty addition but I would start small like 1oz/5 gal and add another addition if you feel like you need more. You can always add more but never take away.