First I sketched out how I thought it should be on printer paper using my Nikon SB-800 for reference.
Some quick folds and this worked pretty well.
After satisfied with the fit, I cut out one side panel to use as a template for the foam.
Then I took an x-acto knife and scored the line, being careful to not cut all the way through.
Here it is test mounted with a rubber-band.
The following are shots with the flash straight on and with the modifier as contrast.
Flash straight on.
With modifier, notice that the details are clearer and not as washed out.
The next two are more subtle.
With modifier, the shadows seam a little more natural. Like I said subtle but an important diference to me.
So I'd say it works pretty well. I eventually want to strengthen the base and attach velcro for mounting to the flash quickly but that is for anothe day.