Negative holders for home-made horizontal 4x5 and 8x10 enlarger

I intend to fabricate a cheap (but hopefully efficient) horizontal enlarger for my bathroom. I have an old cold-light head which I can position at the back of a field camera. The parts still missing are the negative holders. I am at present looking for the type, where two plates hold the negative between them, with pin s inside to keep the negative aligned under the opening. I have one such holder already for the 9x12 format (unfortunately not 4x5), salvaged from an old Linhof 1200, which could be cut down to the standard Graflok size, so that it slides r ight into the back of the view camera, with the groundglass holder removed. I in tend to do the same with an old 8x10 field camera. Here, of course, the groundgl ass holder would have to stay on the camera. With a plain groundglass, there sho uld not be a problem with this. Now to the questions:

Has anyone done this before? Any good tips I could use?

Has any view camera manufacturer had the same idea and already produced such neg ative holders, for 4x5 as well as for 8x10?

Has anyone in this community negative holders of the above kind that they would be prepared to let me have? For 8x10 and 4x5 (especially those!), 2 1/4 x 3 1/4, 6x9 and 6x7? The smaller formats should either be of Graflok type already, or h ave a larger size which I can cut down to Graflock size and the appropriate thic kness (possibly thinner, but not thicker than Graflok standard.

You might consider using mount board, at least in the testing stage. Get a sheet of 4 ply mount board, cut it to the outside dimensions that will allow it to slide into the back of the enlarger. Next cut a hole for the negative that is slightly smaller than the outside dimensions of the negative. Get a piece of adhesive laminating film and stick it to both sides of the negative carrier and cut out the holes for the negative. What you can now do is use a high quality masking tape to tape the negative, by the edges ofr the corners, to the negative carrier, this allows you to pull the negative taut, so that the film doesn't buckle. By using the laminating film, the masking tape will come off of the carrier easier.

It is an inexpensive way to test different carrier configurations, that you can do without any machining. An exacto knife and a straight edge are about all of the tools needed. I have made numerous carriers of this type for odd size glass and film negatives, as well as adapters for 23C negative carriers to my 45MX enlarger.