Timing Curve on 360 in an RV

Anyone know a clever way to confirm I’m at 12 degrees BTDC on the compression stroke of cylinder #1 without taking the valve cover off?

Last time I hand cranked the engine with a finger over the spark plug hole until I felt pressure, dialed it to 12/before on the markings on my balancer, and then used a screw driver to check it was near the top.