re the Butler mod:
It seems like there are a few things they do, but they are not very informative about what all the mods are. However, they do say the best mod is a "deep re-bias." Hey, if you know what that is, please let me know.
I'm just a sucker for mods/upgrades and want to hear it for myself. The designer himself does the mods, so I'm confident that there will be an improvement. The price for the mods is modest, so this is an experiment that seems worth doing.