I can offer you 3 options, and you can use one that you are best with.
1. Click Unfold Undo on the toobars, click on the edges you want cut, and rescale it by unfolding. bad news is you have to re-align the pieces.
2.Right click on 2d window and press Join/Disjoin face. its like folding and editing in 3d, only you see what you do.
3. have someone else do it for you.
dont ask me.