These are my VHW slides, the 3 on the right are all BM bowls, and the one on the far left is locally blown.
Lets start with the standard BM slide (green yellow and black, second from the left) people have been purchasing with a 2.5 cm opening, with and without the silicone ring on the wand.
You'll notice right away that in both setups the wand sits on TOP of the bowl, and this does work. However the seal isnt great, and if you angle the wand at all you will lose the seal.
In this picture the seal has already begun to break, and extra air will flow into the bowl from outside the heat source, which illustrates the sensitivities of this setup and why I don't consider it ideal.
On to the new BM bowls, which have about a 2.8cm opening, what I measured to be the diameter of the wand with the silicone ring on.
Now the wand sits just inside the bowl with the silicone on, with the seal forming on the outside of the silicone ring instead of below it. This works, but even the slight variation between the red and the green bowl (red is immeasurably larger) changes the seal, with the red bowl creating a seal by simply placing the wand inside it, and the green bowl requiring a small twist to make the seal complete.
When used without the silicone ring, the seal is created much further into the bowl, which makes a much more comfortable seal where it doesn't feel like the wand may slip off at any moment, and no special care is needed besides not clinking the glass together roughly. With just myself and people I trust handling glass, this is the setup I've found myself using most frequently.
The screen in the new BM bowls (all 18mm) greatly increases the airflow, and took a little getting used to. While the screen has reduced the vapor density compared to the next slide I'll show, it's also made taking multiple hits easier, and allows more accurate temperature adjustment for scaling up the heat and not getting any scorch taste in the last half of the bowl.
This is the bowl Ive purchased locally, it has a 3cm opening (very similar to the BM bowls, but the final lip opens up and angles outwards while the BM bowls are relatively straight up and down at the top), and I use a glass jack to cover hole on the bottom.
This works very well, about equal to the 2.8cm BM bowls without the silicone for creating a seal, ease of use, and comfort in the hand (aka not going to slip off). The only concern is the glass jack which makes stirring problematic (move the jack on accident and the bowl will get clogged and/or pieces of material will come through) and repacking slightly more difficult (people always lose them in the ABV). But this is the bowl I feel the most comfortable letting other people use, since it eliminates some of delicate handling and doesn't require special effort or attention to maintain the seal. There is a decent amount of air restriction in this setup, which ends up vaping the bowl a little unevenly but also gives you thicker hits.
So it's still too early for me to really comment on which bowl I like more, I've gone back on forth more than once already with which style I like. I will be doing some direct comparison videos this weekend where I will be packing the same amount in each and using the same temperature and hit durations etc. so that should be useful to this process. The 2.8cm bowl without the silicone ring, or a roughly 3cm bowl with the silicon are the two favorites, and I think both have their validity and uses.
The say when I inhale no tobacco is rapidly approaching... Check out my latest thread at OSA for what flavours will go through my new toys... 
Will have to play around with the order for now and see what the others want to do, wait or just get some parts now and make another order later. 
but seriously I NEED to fix my VHW
