Proof

Extended trot would have been perfect if someone had said "Shoulders Back" .  My elbows would have gone back into position and she would have lightened up on the forehand even more.

Extended Trot 

I never go into canter by trotting so fast she has no choice.  I always ensure she is well balanced in a collected trot before the canter transition.  I even throw in at least one walk to canter transition.  

First Canter Stride (from walk I believe)

She's not balanced enough yet for walk to canter to be pretty. I usually do it once and only when I'm getting poor trot to canter departs.

Good Canter

The next two photo's you can see we are both falling apart.  My shoulders are coming forward and she's loosing her implosion.

She's tiring... 

 It was very shortly after this photo that she broke to a trot.  I can see very clearly why.

... and I fell apart 

Notes:  Keep my shoulders back at all times.   Try to transition down just before I\we fall apart.   Be even more clear with the upwards transition - tap with whip if need be.  Turn my shoulders, not my head, to the outside every single time I ask for canter to ensure she steps into the correct lead.