I cant speak for the actual float as I have not had to test it yet
But I will say I am really impressed with it as a bigger guy - lets just say bigger than you. I have had it out already this year a couple times, with my max cold water layering and there is plenty of room, it sits in place really well, and I barely notice it.
I used to have the Lotus P-vest and had the same thoughts as you due to a swim in Gore years back where I went deep and met the bottom so I bought the extra insert for the top pocket that gave you extra float, it helped mentally but I did not think it made a real big difference.
There was a thread I cant find now about high float PFD's (rafters) where a couple people said they used their normal PFD's and then added this and liked it:
NRS Anti-Gravity Shirt
Been thinking about trying it out if I could find it in a store, there is definitely enough room in the Green Jacket to accomodate it, just wonder about how bulky it would feel.