-.08" WC may be too much, how hot does the pipe get? I'd try it at -.06". You have to get it to the best setting where the burn doesn't get lazy (low draft) vs. too hot (high draft) and all the nice heat is going up the chimney. Too much draft will also give you shorter burn times.
Don't forget you need to take the reading and adjust the baro with a full vigorous fire burning and a nice warm chimney.
The hotter the gases going into the flue the more the chimney will draft, so setting it up with a full fire will insure the baro stays closed with a low fire, unless it's responding to the Venturi effect on a windy day. Also a chimney cap will help to cut back on the winds effect on the draft.http://en.wikipedia.org/wiki/Venturi_effect