While I don't have any experience with the units being discussed here, one suggestion I can offer that I use frequently in my line of work (I use small laser rangefinders and occasionally survey grade units in forestry applications) is to set up a crude reflector target. I find Scotchbrite (sp?) reflective tape stuck on the back of a clipboard or small wood panel on a stake allows you to do better at the extreme ranges, and definitely helps in the rain. Obviously, this may not be practical if you're looking to cruise along in a boat and set a line 800 m off shore on your GPS, but if you just need a one-time distance and you can get to the target to place the tape reflector there, it may allow you to get more range out of the unit or at least have it perform to the manufacturers claims. Just another trick to have up your sleeve. It also allows you to be more certain that the laser is indeed reflecting off the target and not something else.