Shaun,
That bow is a good one, the tiller is spot on.
I like the plywood idea for stabilizing the limbs while cutting the splice, it might be easier then the method I use. Currently, when I am splicing using roughed out limbs, I wrap them in plastic wrap, put them in a long narrow cardboard box, line both limbs up, fill it with spray insulation foam, and then let it cure for an hour. Next, I remove the cardboard, true/square the foam blocks (with encased limbs) on the jointer, cut the box in half, scrape the foam off the back of the bow, and proceed with a normal splice. One of these years I should do a splice along but currently the “Half Bow” bucket is empty.