Sorry, Pops, the only compression release I'm familiar with is the systems used on B&S engines, which is automatic and not what you want. Your intent is to be able to shut down the engine normally, glide around awhile with the prop stopped (due to compression), then restart by releasing compression so you can get starting RPM (so, no need for a starter and electrical system). Right? Your idea of an actuating rod through each valve cover, with cams to hold the exhaust valve (rocker) open slightly (could be twist or push-pull) sounds fine. It does complicate valve cover removal (I seem to open mine up often). I'd probably consider the pro/con of this idea vs adding a starter (without an alternator, just a larger lightweight battery good for a few starts).I would like to have some information on compression release with the exhaust valves. Believe a shaft could be run above the rocker arm with lobes to push the exhaust rocker down about .015" for compression release. The shaft would have to be run through the rear of the valve cover ( oil seal needed ) and extended to the cockpit with a handle for the pilot to rotate for the release. Both shafts from the cylinder heads would have to be coupled together for one release handle.