If I'm using crusting buttercream, I just add more sugar and dam with that. Do you make royal icing or can you "stiffen" the smbc somehow? I'd hate, I think, to get a big bite of royal icing in my perfect piece of cake with smbc.

I dam with smbc, fill, stack, then refrigerate. My smbc firms up beautifully in the fridge - never had a problem.

I also damn with my SMBC without any modifications to it. Made correctly, it works great as is. I have never had any problems with blowouts or stability.

Same here... I just use the same SMBC with no modifications at all.

Same as above...except I use IMBC (different method than SMBC).