I have always done gutter mount aiming by sight during the day, and had fairly good luck with that. I am not a big fan of getting on a ladder at night to adjust even though I am also a Christmas light guy. I had a gutter mount this week that was kinda tricky- 10 degree 20 watt going about 40-50 feet to a distant dormer, and after aiming it once, adjusting it after viewing it at night and then still not being happy with it, I figured out a way to get it perfect during the day. we use a green laser pointer for me to tell the guys where to locate lights in trees, and this worked perfect when placed right on the socket inside the fixture. I also laid it on the body without shroud, but you have to make sure it is straight on the body. my next step is to take a bipin base and epoxy a small keychain laser pointer to it for the guys to use at install. I get my pointers and flashlights from dealextreme.com, but remember that green laser pointers greater than 5 milliwatts ( mw) are theoretically illegal in the US and customs sometimes grabs them.