Hi,
I'm not familiar with the 73 but on the EMB170 we have a green dot that is 1.3vs1g. This was going to be flap selection speed but is a little too active i.e. it changes too much in gusts and manouveres(sp) so we have gone to canned speeds. If you want to find best lift over drag look for diriftdown speeds in the aom/afm. If these agree with your green dot then there you have it. The problem you have with a non accurate definition of an indication is something that really should be addressed as this kind of thing can lead to problems.
regards,