It's called "getting a second opinion". Good engineers do it to make sure they haven't forgotten or misunderstood anything when implementing theory. Engine modification is *not* basic and it's entirely reasonable to ask questions about a specific implementation even if you understand the theory and have implemented it before.

You can't "scale down" a large engine like that. The materials are different. Conrods in automotive engines are usually made of steel, which is much more robust than the aluminum used to make conrods for nitro RC engines. Steel has a minimum repetitive-stress threshold, below which it can endure repetitive stress forever; aluminum does not. An aluminum conrod measuring 23.5mm center-to-center will expand .06mm in length when heated from 21°C(70°F) to 127°C(260°F); if the stress-elongation from repetitive loading comes close to that, to say nothing of exceeding it, the conrod will not last long.