7 players on the LOS

I work wing on my crew, and both wings have always counted, and signaled to each other, with a hand on cheek meaning 2 (or 1 in 8-man) on our side, touch the bill of the cap for 3 (or 2 in 8-man), and tap our head (like shot clock violation in basketball) for 4 (or 3 in 8-man). If I touch my cheek and see my other wing tapping his head, all is good. If we both touch the bill of our caps, all is good. We also signal if our last is off the line at the same time.

As HL, I always have the flag if the math doesn't add up. If I throw the flag, and if our U has information otherwise, we'll wave it off. It's worked great, last fall, I think I may have flagged this about a dozen times (mind you, we get some screwy lines in 8-man ball too), and only waved off one because we had a sub on the other wing who screwed me up.