TomD
It should be fun? Sounds like a good plan. Actually the abutments are one of the easier things, and faster things to do. I happen to cut them with Japanese tools because I had them, but anything would probably work pretty well. I have used bow saws. If you don't have the floats, I didn't have them, then it is sorta important to get the cut in on the first go. I just mark the top point on the plane, and then index the lower end off the mouth. I just pinch it against the mouth. I start cutting, and angle the saw to the mark on the top of the plane. I use a flush cut saw to make the cut from the ramp. That is pretty much a gimme. If you want to have the same certainty for the top cut, you can make a wedge, and just rest the flush cut saw on it. That way the cut is pretty much automatic. Flush cut saws are clever that way. But they cut nicely enough I just eyeball the cut. I got a specialized abutment saw from Harelson, and I don't regret spending the money. But for quite a while, I used one of two LV saws.

http://www.leevalley.com/en/wood/page.aspx?p=32933&cat=1,42884,50321

My favourite, the double cut is great for lots of stuff:

http://www.leevalley.com/en/wood/page.aspx?p=32928&cat=1,42884

Once you have the two kerf cuts, the waste comes out easily with a chisel.