Reply by TJU

Here are some pictures of mine. I built it as a prototype a few years ago and just kept using it. The main difference is that mine uses a fence as the guide on the back and the fence can only move along one axis. With this I can mortise any thickness of stock with any thickness of mortise. It is nice to set up for repeatable mortises. I can clamp stop blocks in the fence track to have identical length mortises. I have even taped 4 degree shims to the face to mortise at different angles. When I make a better one I will improve the clamping. Maybe some t tracks with some type of clamps to go in them. The support wing screws off and it is not needed, but I like that I have it there to clamp things to.
I really debated between this type of jig and one with bushings. If I were to use bushings I would need more jigs for different thickness of stock. I can adjust my fence depth to stock over 3” thick (like bed posts).
I never considered using my bench vice. I may have to try that.
Yours looks good. The one thing I would consider improving is your clamping system. It is the one thing that I don’t like about mine. At some point your vertical block that your clamp is on will get in the way. Mine does all the time and it is much smaller. Yours would be nice to have when cuting a mortise in the end of stock but I just use a line to line it up on and that seems to work.

Tim

-- Although the voices aren't real they have some pretty good ideas.