So I had a cabin external structure built a couple of years back.  Been working on finishing the interior myself.  I had originally planned to use vinyl plank floor but as I started working on the stairs I noticed there was a pretty bad dip in the floor.  The cabin is on posts and my first thought was that I was going to have to cry because it was sinking but given that its a dip in the middle and I would expect the loaded exterior to be sinking not the center that didn't seem like the reason.  I got under and looked and it seems like there was a bow to a couple of the 2x10's and that bow looks like it perfectly describes the low dip in the floor.  Not much to be done about it now so I'm stuck with it because the stair support wall landed on that spot.

I think that leaves the v. plank flooring out.  It's WAY too much out to be acceptable for a floating floor.  What are some options?  I think the fact we are talking almost .75" at the worst point means even floor leveling compound would be pretty hard pressed to handle that.  Are there any floors other than vinyl sheet that would be able to live with conforming to that?  Can I try putting in the floor leveling compound and just use a shit ton of it?

Cementitious floor levelers will work in that range. Make sure it is clean and use the recommended bonding primer.

Okay.  That’s good to hear.  I was thinking it might be too much to handle but if i can get it leveled then plank would be better I think.

Agreed with the above poster. I just used laticrete nxt level for my bathroom, I’m building a big ass walk in shower and needed the floor perfect before I laid the pan in. Worked like a charm just use the primer and follow the directions carefully.