Hey everyone - “quick” question. I currently have a standard Langstroth medium on my Flow hive but it’s shoddily made and looks gross so I want to replace it with a Flow sized version. I am cutting down an extra Flow brood box/deep in order to achieve this and just want to confirm I’m doing it right.
If the brood box is 9 5/8" (245 mm) and the medium is 6 5/8" (169 mm), I should simply be able to cut 3" (76mm) off the bottom of the deep, right? And this should leave the correct amount of bee space? I saw the Frederick Dunn video where he did this, but he didn’t cut it at exactly 3" (76mm) - instead he cut it at the box joint, which is less than 3". He said he made his measurement based on the frame depth + bee space but wouldn’t most medium frames be the same depth (when hanging inside the box)? Or is the ledge the frames sit on deeper in a Flow made box than in a “generic” medium? Here’s a pic from the video:
I know I can measure and compare but I was hoping to only open the hive once (when I switch out the boxes).
I hope this post makes sense, but if not, just ignore me! 
Thanks!