I reckon a 5'11 at 34.3 liters would feel very corky for the Ments (though probably ok for a summer beach break board/ groveler). It's all about plan shape and foam distribution and the same volume would be fine if the board was say 6'8.

I am 42 and weigh about 84 kg. I had a custom 6'5 with 35L of float made for my boat trip to the Ments a couple of years ago and I also picked up a secondhand JS 6'2 rounded pin at 32.5L. The 6'2 was my preferred board for the Ments and I found the 6'5 a bit over-volumed for my weight (makes it hard to get a rail in on a step drop) though it does paddle really well.