Baseline height

[gteacher]

The base line is always at the outside edge of the wall top plate at the top of rafter. Top of rafter, at this point, is also the point where pitch is measured & set by Chief.

I don't see any reason for you to try and set the baseline height. Chief automatically cals this for you and determines the birdsmouth cut. For the birsmounth, Chief attempts to use a full depth seat cut matching the plate width, unless the pitch is too shallow. Then, will limit the heal cut. HAP is not given but you can cal it from rafter plumb cut - birdsmouth depth. You only need to set either the ridge height or pitch and Chief cals the other parameters.