Again, what engines use balance shafts? I could be wrong, but I haven't seen one or I missed it when taking apart a rustang 5.0, a civic D16, and a couple of subaru engines. Maybe I wasn't paying attention (quite possible since I wasn't looking for such a balance shaft), but I don't recall seeing anything like that...
If no common engines have that, then there's no point to that being an advantage of the boxer, right? So, do common inline 4s, V6s, or V8s use such shafts?
Joel - unsure of how such a shaft would be of any advantage over counterweighted crankshafts with harmonic dampeners, which would do more than such a shaft would do.