Thats exactly how ive seen the way it will be implemented.
Glad I haven't imagined it!!
So for clarity to utilise all 5 subs, you can either...
Make 1 quintuple substitution.
Make 1 quadruple and 1 single substitution.
Make 1 triple and 2 single substitutions.
Make 1 triple and 1 double substitution.
OR make 2 double and 1 single substitution.