I've had to put off inspecting the HS on my -4 as it's still in the paint shop. I plan to pick it up next weekend and doubt I will be able to bring myself to remove any rivets on the skin to access the forward side of the spar.
The aircraft is almost 22 years old and has over 1100 hours on it, but the HS is brand new. Before sending it to the paint shop, I built new elevators with 0.020 skins and built a new HS to minimize the down time associated with fitting new elevators to an existing HS.
I've been evaluating an integrated doubler/hinge pair that I could locate on the aft side of the spar and rivet in place (w/Cherrymax rivets) without removing any skin rivets.
Here's the part I've been thinking about. It would be machined from a hunk of 4130 alloy steel (same material as the current hinge brackets).
I'd like to structurally bond it in addition to rivets to reduce the likelihood of cracking of the spar at the rivets holes.
This is still a "thought experiment" though it is gaining momentum within the confines of my mind.
Please share your thoughts, critiques, and ideas.