B&W 801 Series 1 and BAF

As the title notes, my main speakers are B&W 801 Series 1 (inherited from my father - I love them). They do not have the B&W supplied bass alignment filter (BAF). The BAF is hard to find, either the B&W one or aftermarket. I do have a bead on a Maughanbox Bass Alignment Filter. The trick is it says for B&W 801 Series 2 or Series 3 and I cannot find anything online that says if it will work with the Series 1. The company no longer seems to have a website.

Before I think about purchasing this item, anyone have insights or thoughts they can share on the Maughanbox BAF working on my Series 1s? Thank you.