I have to wonder if im using the wrong boat model.
Can you tell which is which?
How about from this angle?
I just assumed the porpoise was smaller. And well, it is, a *little* bit, but it's also a little bit wider as well i think.
I used the sargo; pimarly because of asthetics.

I like the lookouts up in the periscope shears, but if you check here:
http://www.navsource.org/archives/08/08167b.htm
You'll see that the Narwhal's shears weren't that high. I could try using the Porpoises conning tower i suppose. I also used the sargo, because i like the ammunition stores being modled, i dont think any other boat model does this.
Another astheric reason i picked on the sargo was because of the aft main deck.

I just think it makes the boat look a bit more special - not neccessarly historically correct. Also, the sargo has the rear netguard for the propellers, the porpoise doesnt, sort of a pet peeve.
There main reason for my examining the porpoise more closely, is because i can't get rid of tubes 7 and 8. The tubes are a data array in the sim file, and i can't edit them out. So i do some micky mouse BS with tubes 7 and 8, or i switch to the porpoise for the historically correct torpedo tube arrangement.