The traveler track obviously conflicts with the standard backstay arrangement. The new setup clears the traveler, provides a 6:1 purchase and is easily adjusted from the helm. It's easier to rig as well.
I picked the 6:1 purchase based on other owners comments and some general advice I found in the literature. Because of the handle and the favorable pull angle, 4:1 would have been plenty. With the fractional rig and the p-19's light mast section, there is only so much force you can apply to the backstay.
In this shot, you can see the control line as it emerges from a hole in the mahogany block and through the cam cleat. The handle is a piece of PVC pipe which snaps into two clips below the cleat. With the line rolled up on the handle and exiting the bottom of the cleat, there is little chance of it accidentally releasing.
The original chainplate needs to be removed. Yet another boat project...
When trailering, we loop a line around the mast, clip it to the backstay and snug it up. It holds the mast and solves the problem of the upper block (not visible) bouncing around.
