Like many, our MH came with a short queen mattress. With the slides in there's no space for anything longer. Neither of us is height challenged, so we've been looking for a solution for this particular "shortage".
We think we found it, so I thought I'd share. We ordered a custom-size foam bolster the width and height of our mattress (and topper) and made it 5 inches long to make up for the missing length in the mattress. We had a sheet-like cover made for the bolster.
When we're underway, the bolster sits on the bed like a big pillow. When we setup, we pull the mattress out from the headboard just far enough to slip in the bolster and make up the bed (with regular size sheets). With that, the shortage is overcome!
We just have to remember to dismantle the bed before we pull the slides in!
We ordered the bolster at Knox Foam
and we have no affiliation with the place other than being happy customers.
Hope this helps fellow tall campers!