1) if you're worried about down shift the overstuff is more dense. I use 40* overstuff like a 30* since I sleep warm I can save a little weight over the 30* and the down is packed tighter and won't move. It's also good for cold sleepers, it helps them reach the temp rating. Overfill can also help in humid conditions
2) widest quilt in the world used to be 48". I am 325# and use a slim in my hammock. I think people use too wide of quilts because they are afraid of feeling one draft at night. If the WM bag is 59" why would a quilt need to be that wide? Also pretty sure the Golite isn't 59". Either way the Golite is only the widest width at one point, mine being half tapered is the full width the whole top half. If you are really worried about it being that big get with my for our XWIDE. It is listed on our sizes info but not offered on our site because it messes all the payment option buttons and tables up. I can do it for around $15 more most of the time and it is 60" half tapered to 46". Will fit any SUMO wrestler ;)
3) no, I don't like offering a product until I have a design that is uniquely mine. I have plans here but I am working to make it mine before I let you make it yours
-Tim