Video camera entrance pupil measure?

Hi:

I´m slowly advancing in my DIY still photo housing. I´m selling my Nikon D200 to start out a housing for a Canon 7D. I´m receiving these days some push buttons and levers from a machinist and will start to work out the housing body (thinking between acrilyc and bent/welded aluminium).

In the meantime I´m thinking with a colleague (my primary job is camera operator, film/video) in assembling a housing for an HDV Sony Z1.

We´re thinking in a first place to try a still photo dome port (maybe a 6´Ikelite) as our front element. I´ve read articles about determining de dome/lens distance regarding the entrance pupil measure. I do assume that is the same with video. I´m trying to find out how to determine this distance in this camera (or any video camera)...

Any clue where to dig the info? Any empirical method?

An idea could be to assembly one simple set up where I could place the camera in different distances from the dome and check the results (may be shooting a siemens star or something similar to easily determine focusing errors).

Any other and simpler idea?

Thanks in advance

Best regards from Buenos Aires

Would be a good idea too if someone using a Z1 housing with standard dome port (not WA dome like the Fathom) could measure distance from inner center of the dome to the front element of the zoom lens.

Thanks in advance!! (I will ask in underwater video too...)