Ok, I've started the trials...
My BM sits over a doorframe and doesn't allow much room for body positioning so I had to separate the two tasks: the muscular part and the finger strength part.
Yesterday I had a quick play at the first part, at the end of a quite serious boxing, farmer's walk and deadlifting session. Not smart, I know.
Anyway I played it very carefully and taking 10 kg off I could easily complete the task: 5" x hang, 90° lock off, full lock off, 90°, hang.
Body positioning was a bit of an issue due to pulley system and boxing bag.
Today I'll probably try the BM part, still don't know how to solve the lack of room problem.
I love this sh*t.