Looks good. It looks like you use threaded rubber feet to position the speaker within the wooden frame (?). I see no acoustical use for the ones on the sides though. Practical perhaps yes but also 8 more places which can transfer vibrations to the frame.

If you use cheap solid rubber feet reaching 90% / -20 dB isolation at 20 Hz requires about 7 mm of ”compression” load (deflection actually as elastomers are incompressible.) That is very hard to reach with cylindrical feet, with conical shaped feet it is more easily achievable. You find more info here: https://www.tme.eu/se/Document/fb716...173/DVA-EN.pdf (The feet I used are hollow "rubber balls" with flanges, quite cheap too and don't need that much of a load to reach quite low in frequency isolation.)