When setting up the 35P (or any other light-screen chronograph) I use the method suggested in the directions, I believe written by Ken Oehler himself:
Set up your rifle on bags, aimed at the downrange target you'll be shooting. Then, with the rifle unloaded and bolt open, set up the chronograph, aligning it while looking over the screens at the muzzle/scope of the rifle. This is quicker than any other method I've tried.
+1
