I'm working on a 2 stroke engine cylinder and I'm trying to model it with regards to the casting houses requirement for no undercuts for the mold.  I'm wondering how I can fill in the attached undercut on the transfer port.  I need it to basically fill in exactly where the red is from the undercut analysis.  I could do it if I could somehow project the profile of the tangent edge of the port as seen in the second picture.  I could then extrude a surface across and fill it in.  Any other thoughts?

Thanks,

Casey