LOL,
I agree with darock... You shouldnt worry about the incidence on a Twist. Its a thumb and eyeball thing..

If you are simply wanting to practice and learn a little about incidences then as he says, level the fuselage as close as you can to the centerline of the plane, and then check your incidences.

If you are wanting to take your work to the next level, this is how the pros check their incidence,,,, with a laser like this [link=http://www.sears.com/sr/javasr/product.do?pid=00948251000&vertical=Sears&BV_UseBV Cookie=Yes]laser level[/link] that will cast a line down the side of the plane so that you can get a true level. Then get an incidence meter and go to work.. I use a digital level like this [link=http://www.sears.com/sr/javasr/product.do?pid=00940195000&vertical=Sears&BV_UseBV Cookie=Yes]digital level[/link] strapped to a GP incidence tool like this...[link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXPW71&P=ML]incidence meter mount[/link]. It gives me deadly accurate results with 100% repeatability.