I just finished my Mechano23 build (but for painting the box). They sound fantastic. I used a port made of black PVC with an internal diameter of 40mm. I had to use slightly different component values in places because I purchased my crossover parts from Parts Express, but I was able to model the effect of the changes using XMechanik's VituixCad project files to confirm the changes wouldn't have a significant impact on the outcome. Total cost all-in was US$296. This does not include box material and I had 0.82uF capacitors on-hand when I started. I also made my own PCB boards using the ferric chloride etching process with leftover copper boards from another build. A wonderful little project.
Below is the VituixCad six-pack of my final measured results. Note that the SPL is relative, I did not use 2.83v specifically.
I did not use any bracing at all inside the cabinet. I took full measurements of the speaker (1) without any stuffing or damping, (2) with 70g of rockwool insulation and (3) with 70g of pink fiberglass insulation. The three near field port measurements are below (separated for clarity). Green has no stuffing or damping, blue has 70g of rockwool and yellow has 70g of pink fiberglass insulation. Pink fiberglass insulation gave me the best result, so that is what I am using in my final speaker.
I made the rookie mistake of changing the depth as a result of using a slightly wider port, resulting in similar height and depth dimensions, exacerbating the internal box resonance at that frequency (see at about 680Hz in the green measurement). I was originally planning on adding internal hardwood strips glued to the sides and top of the box on the inside (to act in place of bracing, in addition to stuffing) to suppress the box resonance, but it was essentially completely eliminated by the pink fiberglass stuffing so I ended up not bothering. All that is left is the port resonance.
Below is the near field port measurement, rockwool v. pink fiberglass (without separation).
And, finally, the nearfield woofer measurement, no damping or stuffing v. 70g pink fiberglass insulation (separated for clarity):
Thank you XMechanik for a wonderful design.