What sheet size?

We have short queen. I took a queen fitted sheet and sewed a 3” tuck starting on a side ( right across the middle) to the other side. This shortened the sheet 6” and it fits our mattress perfectly but you need to try it on at this point to be sure. If ok, lay the tuck flat and stitch down OR do a “flat fell seam” which is similar to the side seam on jeans. Any seamstress can explain. The place where you begin and end this seam may not be beautiful or perfect, but it’s on the sides and tucked under the mattress anyway. My good quality garage sale sheets are much cheaper than specialty rv sheets !