I think this is a great question, just based on personal experience if a sire has a better turf than dirt TGI, and the first time turf TGI is mid-teens or better, for me it's a candidate to be a grass move-up. No data to back this up, just what I've noticed/experienced. I'm sure it depends on the circuit, I play Ny and SoCal. Would be interested in hearing others thoughts and opinions, of course when there is data on the dam that is most reliable but often times if it's a first or second foal the sire data is all we have.
Marc