Just doing lots of work still on the back end.  Scaled everything to within Bullet's .05,10 happy range.  playerCube size is now 1.6 instead of 16.  That fixed some issues I was having with artifacts at high speeds, and being able to escape the level !
Tonight I redesigned the GUI, because it's time I finally started implementing the ability to change settings in-game rather than changing code and recompiling that obj : \
btRigidBody->applyCentralImpulse (btVector3)
This is the method that I'm using to move the playerCube around for now.  I'm trying to avoid use of btKinematicCharacterController.  I took a good look at it, the code is still not mature and a bit unwieldy to use.  Plus it's more oriented towards a traditional character, that runs around with gravity on surfaces with friction, jumps, ducks, etc.  I'm going for a very untraditional approach and gameplay.  Perhaps I will write my own character controller, but I'm hoping to find an easier, simpler approach.  So far, applyCentralImpulse is working quite well, the only downside is the inability to move quickly instantly; it's rather Newtonian.
I think my solution will be to use a non-physics input based movement, unless a collision occurs.  At that moment create the rigidBody, give it velocity, and take away control from the player for a set time, depending on the velocity of impact.  And of course if the velocity is above some threshold, death.