I "skinned" the outer sides
...before addin' the horizontal "fins"
*So, I could "lay 'em flat"
...ta finagle (technical term) the 1/4"MDF around the curves
The top "sponce" has already been "skinned"
...& then, flipped over ta show ya
* Notice I added some extra "backing" behind & just before where the outer "skin" was to bend
This was give me more area
...for "drawing down" & securing (glue & nails) the "skin", to the sub-assembly
...to help manage &/or eliminate any natural "bowing" of the panel, around the curve

Movin' on/next up, was ta make these horizontal "fins"

Here's the plan (pretty simple...really)

Left "sponce" has its inner skin installed
...but, haven't done the right "sponce" yet...ta show ya...the "innards"

Both "sponces" are/have been "skinned"
...& here's about how they will be set up

