Which Viking Mega Quilter is it? They called both the 9" and the 18" the same thing (just to confuse us). The 18" version is made by Tin Lizzie and is identical the TinLizzie 18 LS. If it is the 9" version, you will probably need to remove a queen size quilt half way through and turn it as there won't be enough room in the harp to accommodate the entire rolled up quilt (depends on the batting). Also, you will only have about 4" of actual quilting room towards the end. As to do this, I would rather quilt as you go in sections on my domestic machine.
To answer your other question, I found it a whole lot more intuitive o move the machine.