John, Welcome to the Router Forums! You're in the correct place to find your answer. There is a huge diversity of experience within this group.
Let me say that I am unfamiliar with the sign template set you are making reference to, however; I must ask: are there letters whose parts contain parts of an arrow that you prefer? An example of this (potentially) could be the diagonal segments of the K and the horizontal member of an A - for pointing left. Flipping the K potentially would make this point to the right.
Admittedly, I am "shooting in the dark", but it is all that initially comes to mind for me.
I hope this helps, but quite likely some better suggestions will soon follow mine,
Otis Guillebeau from Auburn, Georgia
OPG3 Tweak everything!