Joe,
If I understand your jig, it is shown without the rail inserted in front of the "mass block", which is used to support the rail as it passes the bit. How do you avoid tearout? When you say "side cut position", do you mean that the rail is set upright on its long edge? If the base is 1/2" thick, then a 1/2" depth cut would be made, right? Further, I assume there is no runner in the miter slot (no screws shown and it doesn't protrude from the back in the second pic), so one must keep the sled against the outfeed block to maintain the proper alignment, right? Maybe another picture or two would clarify this for me and others.
I normally cut tenons on my tablesaw with the rail on a crosscut sled and I use set-out blocks against my fence, too to set a non-binding depth of cut. When I do cope and stick joints on my RT, I also use a set-out block on the infeed and outfeed sides, but secure the workpiece in a coping sled that slides under the exposed bit.