I want to install a skylight to bring light to an internal groundfloor kitchen. The problem is that the only possible location means that the shaft for the window intersects the purlin (8" x 4")in the attic. The purlin supports rafters that are between 8' and 20' long. Is it possible to remove a section of the purlin? If so what kind of bracing is necessary at the cut ends to maintain support for the rafters?