Not reading every post here,so maybe someone covered this already. I took a queen size fitted sheet and sewed 3" seam across about the center of the sheet from side to side. This way I don't mess with fitted corners. When in bed, we don't feel the seam at all. Try it on mattress and see if it fits before continuing.
You have successfully shortened the sheet 6". (3 x 2 = 6). Stitch the flap down at the fold OR cut flap off about 1" remaining. Then cut ONE side of 1" down to 1/2". Fold 1" over 1/2" and tuck under - then stitch down. This makes a " flat fell seam" like the side pant seam of jeans. You can bounce a quarter on your bottom sheet. MUCH better than tucking excess and fighting with it daily.
guy near us sells mattresses out of a little warehouse and he handles 3 grades of "short queen" mattresses. He's $100 cheaper than the one furniture store who sells them. I should get a kickback because I send lots of business his way! We got middle grade, paid $259 and LOVE it. Doesn't even advertise, but he says his phone rings off hook starting May 1
