What about tapering the last 11 inches thicker - to maybe 6 or 8 inches, and before you pour epoxy in dowel pins into the other slab. Maybe use a higher psi mix as well. I really don't think you'd ever have a problem with it unless you plan to drive across it etc.

Side note: we had one of our (just finished unoccupied 2 story house) slabs get undermined by a freak flash flood. It cleared out nearly 8 feet under the corner of two exterior walls. The slab was 4: with #3 bars on 18" centers each way. We could measure no deflection on the walls that met at that corner, and I even stood under it just, cuz.

I wouldn't have believed it if I hadn't seen it, but then again all the old-timers always told me we were overbuilding these days.

Fred. If you're overhanging a retaining wall, is there a possibility you can install steel braces anchored to the retaining wall to support your overhang? I'm no engineer of course.

Dowel pin the two slabs together where they meet. You should be fine. Use good concrete. Mixers are for making mortar for masonry. Good concrete comes from concrete plants in big concrete trucks.