I have done two but never 3 and I have a LA so was able to put it on a rack. Can't imagine trying to manipulate a monster like that under a domestic. Speaking of which, I don't know how many domestic machines out there have what it takes to go through 3 layers like that, especially one being a wool blanket which are quite dense. If you do attempt this, which IMHO is ill advised, I would make a test sandwich first to make sure your machine is even capable of stitching through all those layers. In your test, have piecing so you have the seam allowance as well. I think very few domestic machines, with the exception of workhorse vintage machines would be capable of sewing through all those layers PLUS seam allowances.