With full packing I am floating quite a bit as you can see in this movie. Looking at yet another movie of Herbert Nitsch (he packs 25-30x) where he does his 9:04 WR in 2006 you can see clearly that he is wearing a belt around his waist. According to the new AIDA regulations (v12) using weights is allowed (5.1.3) but the attempt should take place at the surface (5.1.2). I interpret this as meaning that some part of the athlete should be floating.
One year ago I tried a weightbelt but quickly abandoned the whole idea because I could not relax my neck the way I wanted to. I revisited the idea because I'm again doing pack stretches and want to get in as many packs as I can relax with. Currently that is about 10 packs and I think by laying deeper I could probably manage close to 20 so that would buy me some extra time. (sidenote: my 8:02 personal best I did with just 6 packs, no suit, warm water, dynamic training as warmup, i.e. not ideal)
So how much weight do I need? I've tried the weights I currently use for dynamic which is 4kg plus 4.6kg neckweight. My legs were still floating so next time I will add at least 2kg around the waist. Using the neckweight helps me relax my neck because my upper body is deeper in the water making the head drop down less. Or I'll try wearing the Orca suit for (no warmup) static.
... a few days further.... Wearing the Orca suit was a good idea. It's warm enough for no-warmup statics and it is just a little bit less floaty. But best of all I could simply close the neckweight instead of letting it balance on my neck. I did a nice and easy 7:09 that way yesterday. Not on the first, but on the second hold. The first one was just under 4 minutes because I overpacked and was not having fun.
We made some pictures with and without packing and with and without weights that I might post soon to show you how much of a difference this all makes to my buoyancy.