Thanks for the tip, Andy, but I think you are missing my point. Which is: the 4 x 5 enlargers I've used insist that 4 x 5 is the image as framed in a negative carrier. Once you get away from the negative carrier, and try to print the whole negative, you'll find that the diameter of the circular housing of the enlarger is too small to cover the whole sheet, and you'll end up losing the corners of the negative.
At least that's been my experience on three different enlargers, and I'm keen to know if there are 4 x 5 enlargers that have a large enough head to encircle the whole 4 x 5 negative. As to a carrier, I just got two sheets of glass, had the edges smoothed out by the supplier, and hinged them with gaffers tape. That part worked fine. I was just losing my corners (and my mind). Another reason why digital is looking better and better. Thanks, Eric