The Ultralights in the video weigh 6 lb with 24" barrel in 28 Nosler, that's around 7lb with scope and mounts. That's a fair bit less than 8 3/4 pounds. It needs at least a 26" barrel because of the slow burning powder on the heavy projectile.
Agreed there. A 7lb scoped 28 would be quite jumpy. I thought you were saying they needed to be belly guns to be shootable. And while. 26 doesn’t hurt the couple with 24 and 25” barrels worked fine as well. We use a random 25” on our rifles most of the time and it doesn’t seem to make a bit of difference.
