1. did you see the date on that hobbywing page about the tenshock issues? pretty sure that's been resolved. at least if your esc has current firmware.

2. as for the quality of the tenshock motor, are you basing it solely on the fact it doesn't have shims? something that most rc'ers will never have cause to mess with? for me, a bigger issue would be the lack of thread lock on the novak's phillips head (yuck) screws. to me that's more of a "quality" issue than a lack of shims. i also believe the solder tabs are a poor design, but they are sturdy and well made so i'm not sure that's a "quality" issue. i guess you could look at it that way. to me, it's like saying neither one are good quality because they don't have adjustable timing. that's not really a "quality" issue as much as it is just poor, cheap design.

3. i'd check your math on the percentage of magnet volume. i'm getting 60%, which is also slightly off as you didn't take into account the volume of the shaft that the magnets are glued to (a minor change).

4. interesting that the most efficient shimming makes the motor come out just about exactly what the motor is rated (3900kv when divided by 2 to account for the extra poles). kinda makes you wonder maybe the shims got swapped and they are supposed to be how you ended up putting them.