to help reduce stress caused by spinning loads that have high inertia.
This makes no sense to me at all.
The whole concept of CS listers is a large, heavy flywheel and slow speed. Some people put extra flywheels on to reduce flicker. If does not matter if it's the flywheel or rotating mass of the load, they have high inertia as do all of the traditional type generators like you want to use. Never heard of anyone saying they cause " additional stress" ? Additional to what exactly over any other load??
I think I can see what Henry is getting at - the high inertia will resist the power stroke, which means the rods and bearings are seeing maximum stress - from combustion pressure - for longer, than a lower inertia, free-er revving engine. Which, I suspect, is partially why Listers are built like brick sh*thouses; materials analysis was a new thing back when the CS was designed, if it even existed at all, so better over-built than under...
There is a, possibly apocryphal, story about the development of the RR Merlin engine; during the early tests, they'd run the shit out of an engine until it broke. They'd then beef up the bit that broke, and re-run the tests, until something else broke instead. Then they'd beef up that bit... Rinse and repeat many many times, and you end up with an - almost literally - bulletproof engine, which, as we know, went on to worldwide well deserved fame. I doubt the CS went through much of that; they'd just build it waaaay big enough in the first place.