Using 5x4 in my Fotokor

I realise this may not be that easy.. but I think I will give it a go!. Because 9x12cm film is as scarce as hens teeth I have been toying with the idea of modifying one of the Fotokors glass plate holders so 4x5 sheet film can be used..

Problem one: form the measurements I have already done it's clear the focus will be out by 5-8mm.

Problem two: cutting one of the holders down so the side are wafer thin.

Stage 1 go eBay shopping for some double dark slides.
Stage 2 Remove the centre frm a Fotokor plate holder.

http://img.photobucket.com/albums/v613/ColRay04/001.jpg

There is a 6x9 medium format roll film adapter you can sometimes find on eBay, I have one but yet to have any luck to get any in focus pictures on that camera, it's extremely difficult to operate...