Hey,
unfortunately, in my case, i am very limited due to the rather short connection between controller and display.
The cable (loose wires) is secured with hot-glue on the controller side, so for me there was no way to extend it.
But since Jianbo of Vitrolight is quite communicative you could always ask him to make it longer if you decide to order from him.
I don´t know if i understood you right, but before i went the 5,6" way i was fiddling with other display sizes and lenses (including dual 3,5") but found none of those combinations convenient enough (i was aiming at a wide FoV).
Since friday i´ve got the sound working as well, and assembled the unit as good as possible and did some early cable-management. Now i can use the unit quite easily and almost comfortable. Watching movies has been amazing so far, tried some Oblivion and Dirt 2 as well, which was also a nice experience.
But i guess i won´t be using the unit for longer periods of time since eyestrain will definetely become a problem.
I might try to get more space between the display and the lens (right now it´s ~ 2") to achieve the best magnification and probably reducing some of the eyestrain.
Still, i´m very happy with my results so far and i´m definetely in love with my new gadget!
€: Btw, i failed hard at keeping enough room for installing a tracker inside the unit.