I've known Mark Yuhina of FLYINTROPICAL for a number of years now and he's quite an accomplished fly angler. He takes the act of fly casting to academic levels with his experimentation with different fly lines on a fly rod to completely dial it in to his liking.
Mark built this Lamiglas switch rod up a few years ago and recently decided to pick it back up to figure it out all over again. I think he's got it.
Check out his recent post on FLYINTROPICAL on how he decided that 540 grains was the magic number.