I'm setting up a "scanning" rig at present.

I have an old 50D (20mpx) that I will dedicate to this task and so far I've been scanning 6x12cm negs. With the long side of the frame across the short side of the neg I take 4 images and stitch them together. That's nowhere near 1:1 but plenty for most purposes. The end result is a roughly 9000x4500 px image or approx 40Mpx.

I plan to start on my 5x4 as well, and with them I will do two passes at the same magnification, so a total of 8 images.

So far it's working pretty well, yes it's a lot of faffing around but I'm slowly getting the workflow sorted and let's face it, with LF we don't shoot 1000s of photos. Anyway it's better than spending a $1000 or more on a flat bed scanner and the results are at least as good, possibly better. So far I've spent about $10.

There is a gotcha with 120 film though that caused me a heap of anguish for a while with the stitching software

Oh, and yes I use a proper macro lens.