I've long been tempted to get one of the sliding adapters (made by Fotodiox & others) to use one of my digital camera on one of my 5x4 monorail, but I've heard of issues:
Vignetting from the cameras mirror box
An inability to focus to infinity with shorter focal lengths
The area covered is significantly less than 5x4 perhaps only 6x9

Change in focus position from the ground glass to the sensor...
I assume these issues are all worse the greater the registration of the camera being used.
Has anyone tried these adapters?
Am I right about a mirrorless camera working better than a DSLR?
Are there any work-arounds that can be suggested.
I am on the same journey.
There will be issues because you are doing something that wasn't originally intended.
Vignetting: There are tow areas where I have been thinking of the problem.
1: In order to mount the camera on the rear standard, you have to have a tube to bypass the protruding parst of these cameras so as to mount onto the standard in the first place. That tube will cause some loss of overall light hitting the sensor.
2: Short focal lengths.. See above. BUT, what I am experimenting with is a bag bellows. The bag will allow much shorter FL depending on the construction of the LF camera.
Ergo: My old Calumet cc400 the standards and construction even with a bag bellows will not allow anything smaller than 105mm. You simply cannot get anything closer.
The Toyo I just purchased with a bag bellows will allow down to about 50+/- mm lens. (I need to figure out the FD on it.
BUT you have to remember that the distance from the face of the camera moutned will have some depth and thus increase in overall FD.
3: The actual coverage area will actually depend on the sensor size. FF vs APS. The issue here is obvious, but if you wind up with 6 or 8 or 4 pictures stitched together, thats a helluva lot more area than the APS or FF can deliver.
4: See above.
5: I dont have the Fotodoix, but I made a single point of my own to start this with:
The mirrorless (because I don't have one) and depending on the model, may work with a shorter registration distance because it bypasses the issue of the protrusions in most cases (not the Canon FF mirrorless) I think may work very well.
Here is what my set up looks like so far:
I am moving toward a Fotodiox here soon and will mount it to the Toyo.
i simply cannot mount it on my Calumet at all.
Now keep in mind also that the movements also get somewhat exaggerated because of the way its is set up, so you need to make sure you can set it up with the GG or use a live view but that may not work overly well. (Which is why you have to have the Graflok back. )
This is one image with some exxaderated movements, but it is a test shot..
Remember my adapter is stationary so i cant stitch yet. But when that point is reached, remember to have the right software to stitch.
I would say go for it!