@Fine Grind's post about Herbie bags inspired me to take a few photos of my setup. I really enjoy using Herbie bags with scientific glass too but I've similar troubles with the valves on the Herbie bags leaking and having to hold the bag onto the bowl while it fills.
This felt like a lot of effort to repeat over and over. I also really wanted a good way to use my HT with Herbie. I read about other user's experiments creating a GonG connection for the Herbie bowl and tried a few of my own. I finally found something that worked really well.
I took some SSV whip tubing and cut a 1/4" slice of it off. I ran the slice of tubing under hot water and stretched and forced it over the Herbie bowl.
Then I slid a 18mm to 14mm reducer over the top of the bowl, using the SSV whip slice as a gasket for a tight seal. I just twist the adapter tightly onto the bowl.
Now I have a 18mm male connector attached to the top of both my Herbie bowls and can use GonG connectors for everything. I have an 18mm female whip adapter that fits over the Herbie bowl so I can use it with whip too.
For bags, I use an 18mm female to 14mm female adapter.
Then I take a 14mm whip adapter...
...and pop it right up into the valve of the Herbie bag.
I've had no leaking at all with this method during filling. The combined height of the 3 adapters also lifts the bag so it can rest on the opened top of Herbie while it fills.
I never need to mess with the bag as it fills. I just leave the whip adapter in the Herbie bag and pop it into any of my glass I want. I don't have to hold anything and can walk around with the bag firmly attached to my water piece with no vapor leakage.
Next step is figuring out a way to do away with valves altogether and just seal turkey bags to the 14mm whip adapter.