I cut holes in internal parts for a variety of reasons. The primary one is to reduce internal reflective surfaces, the secondary to reduce weight. In the Tubas holes in the cross braces are necessary for an unimpeded sonic pathway across the horn.My current home hi-fi setup of a Tuba 18 sub with TLAH mains (Transmission Line Array Horn) takes advantage of the respective merits of each concept. The end result of full spectrum 99dB sensitivity with minimum size and cost is one that I'm quite pleased with.
With the exception of Snail III all those boxes were pro-sound oriented, as are my DR horns. I'm aware of some people using Snails and DRs in the home, but the designs are less than ideal for that, which is why I came up with the TLAH.