Graphlex Film Pack Adapter Adaptation

My most recent eBay "victory" was a 4x5 Graphlex camera that came with a 4x5 Graphlex film pack adapter. (The camera is fine mechanically, works, and came with a tessar lens for $65!) I want to construct a glass plate insert into this film pack adapter so I can do wetplate collodion 1/4 plates (3.25"x4.25") in it. I think the reversed image on the ground glass from the reflex mirror will be just the ticket for composing ambrotypes and tintypes since they appear laterally reversed when processed

Having never used a film pack adapter like this before, I'm curious as to where the film plane is inside. Can someone who is familiar with these things or 4x5 film packs measure the thickness of the front of the film pack or give me the dimension from the front of the film pack to the film emulsion surface (which I assume is the same distance)?

Thanks for any help.

If I remember right from not looking at my Polaroid pack in a box in the closet, I think that the pack itself defines the film plane. The distance should be the same as a normal holder with film in it. Otherwise, the image would be out of focus.

There is no such word as "Graphlex"!

'There is no such word as "Graphlex"!'

Phorgive me.

"The distance should be the same as a normal holder with film in it."

Yes, but is a Graflex holder made to the same standard as a modern holder? Are the "T" distances the same between a Graflex holder and a modern cut philm holder?

I think the back focus is the same between the two types of holders, and the difference is in the way the holders attach to the camera; the GraFLEX holders have slots in the sides and the GraPHIC holders do not. But the place to find out is at www.graflex.org.