SMR arcs

Quick question, couldn't find it in the rules.	Do SMRs have to
be the 3 F arcs or can I assign them different arcs?  With
the Rolling rules AP FP F arcs make sense to me.  I've also
decided to pay the extra mass factor to have 2 SMR's vs one
SML with two shots.  That looks like the difference between
saturating defenses and having no affect.

Roger Books