Other than packaging issues and scavenging oil out of the heads, pancakes have a lot going for them. Not just weight distribution but for a 4-cyl, if you put con-rods for opposed pairs on the same crank bearing (like a radial), do the same with the second pair you can mostly cancel secondary vibration (one set goes up while the other goes down).

Speaking of radials, aages ago (late 70s?) I was walking through a Sikorsky factory floor (CT). Near the entrance, there was a demo / cutaway P&W R4370 on a stand. You could actually rotate the crank by hand, watch everything move in the cutaways. They had to send somebody out to come fetch me to the meeting that I was in that building for.

One of the guys on the floor, seeing my interest, got me involved with a P-38 restoration that was ongoing nearby (close to Bradley). I heard somebody say "yeah, another one." so I don't think I was the only person waylaid. Kid. in. a. candy. store.

More generally, there's a lot of interesting engineering that's come out of that era Italy. I see what they were doing a bit like the Brits building steam engines in the late 1800s, working around material limitations (e.g. Brit. asymmetric thread design to deal with high pressures and poor steel and Italian hairpin valve springs for the same reason).