When I was deciding on the radius for the top of the side panels I was looking at the drawings, but was always
drawn back to this photo of the flat packs offered by Danny.
Notice how the panel tip protrudes past the back of the sub box, looks like a couple of inches.
On your sketch it shows the tip finishing even with the sub box.
I think this is because the flat packs were modified to allow more room (height) for the x-over box.
You can see this comparing your sketch to the picture below.
I also think your bottom radius cut should not come in so far, it should be at the point where the top box is.
This would help with your longer back leg.
Again you can compare to the pic of the flat pack.
So considering that the panel passes the top of the sub box about mid point (yours might be a bit shy of mid)
this would make the cut of the top round longer ....I worked on this for a long time before I came to a decision
on exactly what I would do, because I had to take into consideration the extra width (2") of the sand filled bottom baffles.
So you have three points to strike the radius with. (1)The top (2) the point where it intersects the top of the sub box,
(3) how far past (if past at all) from the back of the sub box.
I did what you plan on doing with the template, then using it to router out the side panels.
I build a lot of round walls and barrel ceilings in my job and I was wondering how to strike the
radius. I finally just took a flexible 3' steel ruler and bent it to the 3 plotted points, then traced.....worked like a charm.
These builds are just a lot of fun......especially from scratch. Have fun!
Pic of the flat packs assembled:
