At the stage of final installation. Only to have one bump in the road. Finding out that I won't be able to squeeze in the second battery in the cavity control area. And I don't wanna do any routing on my bass. So I'm reaching out to see if someone might know, if there is a big change in the output and headroom changing it from 18 to 9v. Please let me know when you have a free moment for input on this related post.