Just boxed one of each of these up in separate enclosures. They both work wonderfully individually, without the envelope jack enabled. But when I do have a cable inserted the Junk Trunk only sweeps if the Gas Tank is also engaged. Otherwise, it's just a fixed wah.
I'm using these jacks - https://smallbear-electronics.mybigcommerce.com/1-4-in-stereo-nys212/ (https://smallbear-electronics.mybigcommerce.com/1-4-in-stereo-nys212/)
EDIT: I used the wrong bypass scheme for the Gas Tank ::)