Have done so once. If material prewashed not a problem.

Me, too. Gabeway is right!!

I always trim the selvadges, they will shrink differently than the fabric. Won't you still need several inches around the quilt that will be taken up when the quilt is quilted?

I've done it with good results but only in an emergency-----what you have IS an emergency.

I have used selvages, but do take some off. I haven't had any problems, but then I like my quilts squishy and vintage looking. I've not noticed the selvage looking any different.

Oh I would not do it, the selvage edge has no give to it. Your project will most likely buckle.
I snip the cut edge about a half inch from the selvage edge then grab and rip the fabric. It will rip in a straight line, if you don't plan on saving your selvage edges in some cute slevage project then save it anyway, its great (very strong) rope for tying things...like tomatoes in the garden, boxes for recycling etc. Best thing is you know that you have a perfectly straight edge.

The main reason to trim off the selvage edges is that they are more tightly woven and will shrink in a different way when washed as well as being somewhat harder to quilt. I usually just take a nip in the fabric next to the selvage, then rip. If you feel you have to use that little bit to make the back large enough,then definitely take snips in the selvage every couple of inches or so, similar to easing in a sleeve in a garment.

I have done this in the past and have not noticed any problems. Interesting question though.

I think you are asking for puckers if you do.

I would be more afraid of the backing shrinking and pulling in when it's quilted than I would be of leaving the selvedge on. I would cut the selvdges off and add a border on the backing if it's going to be that close to the size of the top. Quilting shrinks the backing and the batting and you may end up with the top overhanging the back.