There probably isn’t a hard number on your boat because manufacturers are not required to certify the number on boats over 20’. I don’t take more than 4 or 5 on my bridge depending on the conditions. Look up the story of the 34’ Silverton on the 4th of July several years ago. It was grossly overloaded and things went badly in an instant.
On my Mainship 34T which has as wide a beam as the 40 and a huge fly bridge, I would have 8 or more on top at the dock, 6 in light seas and only 4 or less in 4' seas or greater.
If the seas are rough enough to matter nobody will want to be up there..
As a whole I go with if there's enough room for butts to sit you're good but everyone standing around and leaning could cause a problem to fit more people than intended.
(L X W) / 18 = Total # of passengers of which 1/4 or so should be on a flybridge.
My mainship works out to 34x12/18=23 max passengers which would be 4-5 up top. I've had 8 in rough seas with no effect but 23 passengers sounds like way too much.
I had 5 on our 390 in 5-6' seas. Two of them went down below after an hour or so. Too much movement. I've had as many as 8 up there on very calm days.
John
I fell like a wimp I'm on long island sound in New York and 2 , 3 ft seas are more than enough for me. I go out with 6 to 8 people the most. I use my boat for day trips and live on it during the summer.I love the boat and summer joy it brings. Tom