[tremrej65]

but it's also much thicker than the standard flatpack

It look thicker but it is not: the flatpack is 1.5 inches sides, top, bottom, and 3/4 for the middle separator. Mine is also 1.5 inches all around, and 3/4 at the intersection of the 2 tubes.
Right now, I would say the bigger problem is the vibration in the front/back direction of the top of the cabinet. At high volume, when I put my hands on the side of each tubes, there's more vibration on the top one. This is noticeable. I imagine you get the same effect with the standard flatpack and most likely worst on the 3 woofer version. A larger base might mitigate this issue a little bit. The effect is minimized when I add 50 lbs on top of the cabinet. See picture below.
Nevertheless, the bass is super tight, super controlled. I really like it.

[Danny Richie]

Right now, I would say the bigger problem is the vibration in the front/back direction of the top of the cabinet. At high volume, when I put my hands on the side of each tubes, there's more vibration on the top one. This is noticeable. I imagine you get the same effect with the standard flatpack and most likely worst on the 3 woofer version.

The opening on the H frame variation is larger. So the pressure within the H frame is less. Then with the addition of the No Rez on the panels, there is next to zero vibration of any kind.

[robwm]

What an amazing build! Thank you for sharing!

[ketchup]

It look thicker but it is not: the flatpack is 1.5 inches sides, top, bottom, and 3/4 for the middle separator. Mine is also 1.5 inches all around, and 3/4 at the intersection of the 2 tubes.
Right now, I would say the bigger problem is the vibration in the front/back direction of the top of the cabinet. At high volume, when I put my hands on the side of each tubes, there's more vibration on the top one. This is noticeable. I imagine you get the same effect with the standard flatpack and most likely worst on the 3 woofer version. A larger base might mitigate this issue a little bit. The effect is minimized when I add 50 lbs on top of the cabinet. See picture below.
Nevertheless, the bass is super tight, super controlled. I really like it.

Are they on carpet?  If so, do they have spikes that go through the carpet to something solid beneath the carpet?  Without music playing, are you able to rock the subs by pushing forward or backward?  If you can get them coupled to the subfloor, I don't think they'll move much.

Awesome looking build, by the way!