Would anyone out there in timber frame land choose to share their favorite methods/templates for cutting housings, particularly blind housings with a router.

I am on my 5th frame, the first 3 being fully scribed but have just finished my first square rule frame and have another on the books. Quite frankly cutting blind housings with a chisel is driving me mad. It is the sort of job machines were made for.
I have tried playing around with a square cutting bit with the router held free hand but am not happy with the level of control. I have had a bit of a look at router jigs out there and they all seem to rely on using the base as a guide.
To me a pattern cutting bit with a template the same size as your housings makes the most sense.
Are there off the shelf, adjustable pattern cutting jigs out there? Do you make your own? Do you have a separate jig for each standard housing you cut?
Would love to hear your ideas.