Okay, Okay, Baer. I whacked it, layed it, stopped screwing time, sucked it up and got it done, almost. (For anyone who wonder where that came from, those are not my words, see in "Pajama Grumbling", Baer's reply scolding me for procrastinating and whining about it)
Aaaand, I marked it before I underpinned it, and didn't even see your warning until after I got home. Good Girl, Lassie.
I found a nice coved moulding that fit the wide sides and ripped the other 2 narrower sides. No table saw, had to do it with a hand saw...that wasn't fun, but it worked. Only problem was narrow side also is the shallower side now, in that the tallest part of the coving is cut off and there's a gap under the rabbet of the frame and the liner on those 2 sides. So, I have to build back up the coving toward the back, then wrap with the fabric in the morning. Didn't weight the bottom. Will experiment with that another time, ripping two sides by handsaw was hard enough. Ran out of steam.
Will let ya know how it turned out, and maybe with the earlier thread on how to post pictures now, I can even figure that one out!
Thanks everyone, for the help. Seee? All I had to do was ask!