On a speed run in moderate conditions (Like Lake George most of the time) you can almost not have the outhaul too loose. A few years ago I experimented on a pretty consistent day at Sandy Point in about 26-30 knots using my 5m Koncept on the speed board. Every run I let it looser I went faster. Even when it was bagged out so the batten was reversing over the boom and the sail was starting to wrap over the boom right up the the front harness lines. Of course, it was horrible if I tired to sail back upwind like that.

. It was also pretty hard to control on the reach run in to the run.
Part of this is probably because I choose to sail on a slightly smaller sail than I could get away with a lot of the time. I find this is faster for me in most conditions as it lets the board fly better.
In the end, I settled for letting the sail touch the boom about 2/3rds along towards the front. But in winds like a couple of weeks ago well into the high 30's and gusting well over 40, I was on the edge of loosing control in the big squalls, with the batten just touching where it crosses the boom on my 4.7m KA Speed. I was definitely not thinking I would bag the sail any more!

. But in these conditions it is very difficult to sail upwind, and mostly not worth trying. It's faster, safer and less energy sapping to walk back at least 1/2 to 2/3rds of the way. If the angle is good, I walk all the way back. In winds where you have to sail back upwind, it is a big advantage to be able to flatten the sail, because is you are powered up to the max at 135 off the wind on the speed run, you will be waaayy overdone for sailing upwind and will need to dump as much power as possible.