With current computer engineering, it appears to be possible to make pretty much any engine configuration work (balance) long enough that other part failures or service intervals will become more important. Either with use of balance shafts or without them. Sure, good primary balance probably results in less compromises during the design phase, but inline 4 cylinders aren't much better.
All engines are compromised one way or another. Pistons shooting up and down a cylinder connected to a crankshaft with controlled explosions as a propellant are always going to create some vibration concerns in the long run.
I think your dad has an overly fundamental view in his belief that the Triumph 3 is troubled by nature. He needs to read up on more advanced engineering techniques.
). . . we're caught in the moebius loop now! 
He actually missed an R as well, which was what I was talking about, not leaving the s off the end.
