All things being elastic

You could also try sheet stays/suspenders. Should keep the sheet held on a little more effectively. And if you do size up it should help take up the slack if the sheet is loose

Yeah, i think i will order the a set of the one up bigger size, that should also eliminate my annoyances with the flat sheet being precarious to even ly drap over everything too

Good to have some room for redundancy as opposed to a perfect fit which has no value to me if it impedes movement—which it pretty much always will when my bed is in extreme odd positions

Edit - ordered king size set so will keep that suspender thing in mind if i find the set to be unruly—"we" shallt see