I guess I do not understand what is going on.  A Tower Hobbies Pro .46 is a lot more engine than an OS 40 FP.  Generally, the TH is a screamer especially when used with the Tower Hobbies muffler.  It seems to me that a 10 X 7 on a TH 46 is under proped to me.  The standard for that engine ought to be 11 X 6.  So I am thinking the engines are showing their age and the Tower Hobbies probably needs new bearings, there is no bearing cure for the FP as it is a sleeve bearing engine.

And I think any stumble on acceleration indicates the low end is not acceptable.  It indicates to me that the low end is not set correctly.  If acceleration test is your measure, then you have failed. 

I do not use a pinch test.  I use a TACH, and acceleration test.  If it has a smoke trail that is okay.  But I do not worry too much about smoke trails.  Smoke trails indicate to me that there is some Castor in the fuel mix and that is a good thing.

But then I do not shoot for the max, I try to get a smooth running engine and take the performance given.