I'm not faulting a 7 main straight 6 just saying there are consequences of the design (ie, it has more crank torsional displacement than a v8 or v6 etc.)What I was saying is that the crank could elastically twist in torsion and put the cylinders out of time in relation to one another. This crank has the same main bearing diameter as the m103 but way more loading (both reciprocating mass and compression). In any case agree to disagree.
Check this out if you like.(good bed time reading)
http://bc.biblos.pk.edu.pl/bc/resources/CT/CzasopismoTechniczne_8M_2008/MitianiecW/TorsionalVibration/pdf/MitianiecW_TorsionalVibration.pdf
Sort of interesting that a straight 6 has the first torsional mode well within the rev range (and quite a large magnitude compared to actual engine torque) at that the conclusion is that the damping is mainly acheived by cylinder wall friction. Of course our motors have a harmonic balancer so point is probably mute anyway. Sorry about the tangent. Doesn't have much to do with my original theory.