Mike,

It would be interesting to see Don's notes.  Here is my take on the effects of the T:
1.  Reduces rudder sensitivity around neutral
2.  Adds yaw aurhority
3.  Pushes/pulls/ all lock on a little better
4.  Gives "carve" in yaw instead of "skid"
5.  Small heading corrections easier to apply
6.  Adds positivie pitching moment with rudder application - how much seems dependant on how tall it is
7.  Doesn't affect roll mixing
8.  Plane will deviate less from the intended line during rolls or point rolls
9.  CG assessment - allows you to fly a nose-heavy plane as measured statically, but in flight it will  "roll" and maintain 45 lines like a more neutral plane
10. Elevator - maybe some more pitch authority but not a drastic difference
11. Stall Turns- some can feel a difference, It is barely noticeable for me
12. Spins/Snaps - uneffected for the conditions I fly (snaps high rate aileron, spins, full rudder/elevator, tiny aileron).

Abbra  -mid wing, Aggressor, mid/low wing, Osmose, mid/low wing, Passport, low wing.  The basic effect was the same for each of these planes.  For me, it just makes the FAI maneuvers easier and less work.  I've also flown the Passport with YS 170, now with CDI, Electric (with and with our SFGs).  T-can and no T-can, used the CA models T then made my own when I lost the original - even with small dimentional changes to the T nothing was changed as to the effect it provided the model. 

It may be different for the VF3 though.  You've had a lot of input on the plane for the past couple years for sure, and congrats also on developing a new bird too.  Nothing to relax about here - airplane trimming and setup  is one of the best parts of pattern to me.
Thanks,
Jim