It was difficult to tell when I tried this morning, there certainly wasn’t any increase when the sub was turned up to max, there was a slight vibration from it but I think that was just vibration from the other speakers bass output hitting it, like it was acting as a passive radiator (going back to my Ferrograph/KEF days!).
I’m hoping someone on the FB group lives near enough to compare. I’m certain it’s not working, everyone who has one says it’s enough to vibrate the boot and mirror (like my previous Honda). Mine certainly doesn’t.
Please excuse spelling/typos. Apart from being a clot it turns out I had one on my cerebellum that's now causing various problems!