Greets!

You're welcome!

No, I missed the 'step' in the cutout.

Not really, just stick some thick enough felt or similar pads on the 'steps' to snug it up.

At 16+ ft^3, a couple of 10ths off either way isn't audible.

I guess not other than I don't see any provision for easy vent tuning. It's location is fine.

Yes, this is my insulation of choice same as Altec after the asbestos laced Celotex was outlawed. Many manufacturers, DIYers use polyfil and the material properties MJK uses in his software with lamb's wool being considered the Rolls Royce of speaker damping.

Then there's open cell foam now that they've learned how to keep it from dissolving over time. I've experimented with open cell sleeping pad since it's so cheap at the local Wal-Mart, K-Mart, Cloth World or similar 'big box' discount stores. No doubt there's other materials out there and seems to me I read something awhile back about 'green' ground up T-shirts or jeans or some-such, so with each of these having radically different damping coefficients, you would have to experiment to find the optimum amount.

Just don't use closed cell foam..........

GM