Some pretty strong comments-
The business about the crankshaft comparisons really seems odd tho -
Let me see if I understand that part only-
We take a 5 piece crank
1.front shaft 2.throw plate 3. rod journal 4.throw plate 5 . rear rear shaft.
and we install all of the pieces togather --including the con rod.
OK let me back up - lets sat the front shaft and the plate are machined from one piece - ditto for the rear shaft and throw.
now we have a three piece crank.
OK we assemble all of this.
then align it
Do we weld it togather?
If we get a bad crash - will the 5 pieces or three pieces get out of line?
The chain saw engines I have seen over the years - do get out of line or bent or both at this part of the assembly.
Is this assembly stiffer than a properly designed cantilever single crank?
If so - how?
Lets do a firing cycle and look at what is going on.
the piston is at the top and the firing occurs.
the downstroke now applies a bending load to each side plate (counterweight - whatever you choose to call them,.
each shaft front and rear now deflects up at the ends.
OK -you say "no it does not!"
How can you prove it?
If the prop is horizontal when the piston fires (90 degrees to it)
- the prop offers no stabilizing load .
If the prop is in line with the crankthrow - it will help stabilize the bending load.
If this test assists in reducing vibration, how did it do it
Hmmmmm?

On some twin cyl designs which had no dual bearings on the front of the crank - this shaking and the fix was noticable.
Perhaps not all of them - but it occurred on the ones I saw.
We are concerned here with the single cyl engine- so-- I will stick with that.
Now lets look at a modern cantilever crank for a single.
The typical one is first machined from a chunk of steel - the whole thing.
Some are made from one chunk -minus the prop screw
Some are machined, then the crank pin is forced into place.
Anyway - the "crank assembly" is now ground and hardened -and polished to extremely tight tolerances -
This assembly is fitted into two bearings -which hold the shaft in line.
Now the firing force does push down and -yes slightly of the rear bearing center.
can this shaft bend?
Where -?
So - is this the off center load which makes this an inferior balance setup?
Have you looked at a modern cantilever crank having additional heavy metal inserts which overbalance to provide smoothness?
All of the smooth vs not smooth I have tracked down on single two strokes (two cycle)-has proven (to me) to originate in
A-the compression
B- the prop/spinner -etc.
C-improper timing and or fuel.
That is Gas -or Glow
Please note I am not condemning the chain saw type cranks - these work -and have worked for years.
I am just asking WHY you can consider them to be an advantage .
Now here comes the hard part - but I will say it anyway.
From an evolutionary standpoint -in single cyl model engines the cantilever style crank is the accepted current setup for all of the high performance designs I have seen.
If you take note of any of the most modern European -or Japanese model two strokes - again the same setup.
However--IF we had con rods with end caps which would allow the removal /replacement of the rod assy's --and also permit the final assembled 5 piece (3piece crank/) to be perfectly ground -hardened balanced - I would say - it is a set up for models engines I would like.
As far as power output - I will not comment except to say that the trend to quiet efficient exhaust systems are the wave of the future for some - and the current setup for many others .
the "downspout" exhausts are fading fast -and for engines with high cylinder pressures - will fade even faster - why ? Noise
For lower power output stuff - low compressions and low exhaust bark - they will be more acceptable.