Do It Yourself Handcycle: Building the handgrips / pedals

For me, the pedals of a bicycle become the handgrips of a handcycle. For my handcycle, I am building these from scratch since there is no commercial product that matches my specs. Those specs are:

The right handgrip must contain the gear changing mechanism for the hub transmission.
Both grips must accommodate brake levers (Often only one grip contains a brake lever since the second brake on a handcycle is normally considered a "parking" brake. I consider this layout inherently unsafe).
Grips must not be constructed to be out beyond the width of the knees (as many handcycles designs do). I would like to keep a more aerodynamic shape to my body. One can imagine the disadvantage a time-trialist or triathlete would have if their body position required that the hands be well wide of the knees.
The bearings must be easily replaced.
The grips must conform to the hand. A cyclist can only image the discomfort if the cyclist had to put in a century without shoes. Even if the bicycle's axles are big tubes in order to have a larger surface area against the foot, the cyclist would soon find discomfort in his/her feet anyway. For me, my fingers cramp up quite often.
The grips must have a fairly large surface area.

After I built the tubes (previous post), I fitted the tubes to one another and to the urethane foam plugs that represent the grip's forms.