The Anaxilus template should be fine. The thickness of the velvet I'm using is 1-1.5 mm (hard to measure), but a little thicker (if that exists) wouldn't hurt. For the ring I would recommend to use just one layer, the rear frame bar deserves 2 or 3 layers, one attached on top of the other by means of a strong double-sided adhesive tape or foil, e.g. carpet tape (also to keep the fabric pieces in shape). It's a good idea to add some less sticky adhesive tape to the underside with contact to the plastic frame to facilitate the removal.
I've decided for black since it provides considerably higher light aborption. Thus it's not unlikely that it also provides better sound absorption than white (let's say by 5.75%), since light absorption happens by diffraction within the fibre structure, and the same could be valid for sound waves.
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I hope my EQ curve for the velvet-modified HD 800 is of use for you (at least as a nonbinding template considering the chance that your individual HRTF may differ from mine):
This in view that my two pairs require significantly different compensation curves. Above curve is for the older pair. The newer pair, although brighter, needs a stronger increase of the upper treble.
The equalizer used is
xnor's Graphic Equalizer for
foobar2000. (While I guess your «PEQ» stands for «parametric equalizer».)