I am slightly confused by what you have there. In your right hand is that the whole LCD assembly and that is just a stainless steel box you made?
I can see the inverter wires comign form the edge of the think in you hand.
The backlight works as follows: Perimeter of CCFL light shines sideways intio the plexi light guide. This light guide has a texture pattern ont he back so the light leaves the plexi at the rear. It then hits a white reflector ands bounces back out straight through the plexi - through various diffuser sheets and polarizer sheets (may be refelctive) and throught the LCD.
the 16 bulb is a lot. you want to concentrate on the total length and getting the light distribution as even as possible. The plexi does that perfectyl as the CCFL is shielded from directly shinging through the diffuser and creating a a bright edge. We are cramming so much tube in there we hope it will be nice and even whent he diffuser do their work. If not we have solutions to try.
The diamters you see gve out different light intensities. ie the smaller tubes have a hight cd/m2 but over 1 m a larger diamter has more surface area so with the lower cd/m2 rating gives abotu the same output.
The smaller tubes are just more compact but they do have a lower life and the running voltage is slightly higher. The larger bulbs however are available in longer lengths. The running and starting voltage goes up with length so to get the same amount of light out of a wide tube you need to have it longer and thus need higher voltages as this outweighs the lower voltage from the smaller diameter. It is trade off with tube life, diameter/length and running voltage (and starting voltage as a long thick tube may be damn hard to start as you need 3000V).
LAST PARA EDITED AS I WAS HALF ASLEEP.