Well, I can do that! I haven't seen the Casita but if it's anything like the
Scamp, there are two ways to do it. The easiest is to take a plain white sheet (preferably ironed so size is stable), center it over the existing cushions, and tuck the excess neatly all the way around the cushion. Then take a washable kid's magic marker and follow the contours of the cushions as they exist (washable because they bleed less - check to be sure it doesn't bleed through to the cushions). Remove the sheet and you have the exact pattern of the top. Add seam allowance as desired and, viola, a pattern. This could also be done by securing the sheet to the bedboard with double sided tape but that gets a little funkier because the present cushions have already made an allowance for fitting room inside the shell. Hope this is what you wanted! :wave