I've been doing it this way for years...in fact, I've never done a bed-quilt entire. I design all my quilts, so it's easy to plan the quilt to facilitate this type of construction.
Just draw your design so that you can construct in quarters; they don't even have to be equal in size; a quilt that is 5 by 6 squares can be constructed in 2 sections of 9 squares and 2 section of 6 squares. It's all the same in the end. Quilt each section....so much easier to handle (I do all my quilting on a little table).
You can even plan your inner and outer borders accordingly to work out in each section. When all sections are done, I pin back backing and batting and sew sections together so the top is matched and stitched to make the divisions invisable. then trim batting up to the seam line in back and fold backing over the opposing section of backing and batting and tack down in small, even stitches. It works! And it holds up ;
my favorite old quilt on my bed is good as new even after several years of use. Hope this helps!....Mary