In my experience one piece is the way to go for buoyancy reasons. As soon as I add a second layer I cannot add enough weight and fight buoyancy the whole dive.
I have a 7mm two piece farmer john, a 5mm one piece with a second 5mm sleeveless jacket that can be added and a 3mm one piece.
In fresh water I can dive the 3mm with 4 pounds. The 5mm with 8 pounds, which I can probably trim to 6. When I add the second layer to the 5mm I can go up to 12 pounds and have to swim to get down and fight to stay down.
The 7mm two piece the least I have been able to dive is 16 pounds, again have to swim to get under and fight to stay down in shallow water. Then once I get to depth I have to start pumping air.
With all that said, I am now saving my pennies for a dry suit.
I have a 7mm two piece farmer john, a 5mm one piece with a second 5mm sleeveless jacket that can be added and a 3mm one piece.
In fresh water I can dive the 3mm with 4 pounds. The 5mm with 8 pounds, which I can probably trim to 6. When I add the second layer to the 5mm I can go up to 12 pounds and have to swim to get down and fight to stay down.
The 7mm two piece the least I have been able to dive is 16 pounds, again have to swim to get under and fight to stay down in shallow water. Then once I get to depth I have to start pumping air.
With all that said, I am now saving my pennies for a dry suit.
