The forums, internet and NTSB reports are chock full of engine failures at some short time following the invasive procedure of changing a cylinder or on up to a top overhaul.

In order to change the cylinders, the crank must be turned to orient the connecting rod to such a place in its travel that allows for the piston and piston pin to be assembled onto the rod. While doing this crank movement and having little or no clamping force on the case through bolts, it is possible for the crank bearings to "spin" or shift in their locations. Some number of hours later.....yup....BOOM! Then you're a glider doing a for-real engine out in your Bonanza or getting a live S/E workout in your Baron with oil all over your windshield or nacelle and a gaping hole in the engine case!

Check out what Mike Busch, the Savvy Aviator, has to say about Top Overhauls & cylinder changes HERE.

Many experienced engine guys I know recommend and use "Torque Plates" during their cylinder R&R. These plates apply clamping torque in much the same way as when the cylinders are clamped in place on the through bolts.

Below is an example of a simple torque plate. I don't know about you, but I'd sure feel a lot better seeing this on my case when cylinders are replaced.

Below are suggested dimensions for a simple torque plate.

Download a SolidWorks drawing zip file HERE

If you have some old cylinders laying around you can cut down the bases and make some pretty spiffy torque plates.