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Join Date: Sep 2005
Location: New Westminster, BC
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Using flat sheets and making do works, but some berth dimensions do allow the use of fitted sheets, they just don't fit perfectly so you tuck the excess away.
We use standard bedding linens and a quilt top most of the year in our aft double, which is a decent size.
For single berths (kids and guests) we used flat sheets doubled over and tucked under, making almost a sleeping bag style where the single sheet serves under and over.
Of course, for little ones sleeping bags work well as long as they are not too slippery on the outside (makes for little bumps in the night)