A very effective method for cutting sharp angles on the hard board is to tape the hardboard to a larger piece of lumber (2x4 or 4x4) with a GOOD QUALITY double sided tape. Like this:
http://www.woodcraft.com/Product/15D...-x-36-Yds.aspx.
Set your blade to 16deg make several small passes until you have the right depth of cut. Gently remove hardboard, use a butter knife to slide between the pieces.