As Mike alludes, a limit switch may be a better answer, and as you yourself noted it likely already exists. Again, perhaps by calling HWH you will know where it can likely be found and whether moving/adjusting that switch to match the limit strap maximum is advisable. The camera notion, placing it in the midst of road debris, dust, and muck, just doesn’t seem the best option.
My brother-in-law was a Weyerhaeuser millwright, a natural engineer with a 5th grade education. When the coach was new and I mentioned to him the rear raise limit issue, he immediately retrieved an old, long automotive cable (throttle or brake or something and with a handle on one end) from his garage and explained how its wire end could be fastened to the front axle base structure. Routed through the floor, with the cable sheath fastened to the dash somewhere, and the wire configured with a maximum mark, one could tell from the driver’s seat when the body was at the top of the rear limit straps. The core wire with top handle would stay put while the sheath went up and down with the coach body.
Not anxious to drill holes in the floor pan of our new coach, I stored the cable away somewhere and never expedited his idea. At 94 he’s probably forgotten about the notion, but it’s still a simple mechanical solution involving no electronic gizmos to go haywire.
Joel