Open field distance does not matter much except perhaps on par 4 or 5 holes where you can just crush it in an open fairway. The real meaning in this question and for that matter any question regarding your "true golf distance" is primarily three values. How far can you throw a hyzer or hyzer stall in a reasonably wide fairway say 40 feet wide? How far can you throw straight or a shallow S-flex, again 40 ft wide? And then how far can you throw either your anhyzer or forehand, again in that 40 ft wide fairway?
Yes, you could substitute thumbers for any of those shots but no rollers since you can't always count on good ground. I'm thinking the average of these three numbers or literally tracking these three numbers separately would be a more accurate gauge of your reliable golf distance. What you need to do is find accurately measured holes long enough as reference points or artificially create them by throwing closer to the edge of fields. I'm probably a 315-335-295 in summer.