Unfortunately there are tons of inaccuracies and errors existing in the OR's. Its a good starting and reference point for most recorded events, but definately not infallible. Many writers and researchers use it like the gospel as the absolute. Heed great deal of caution on that one...

Torpedo types;
There are a host of different reported accounts of what the Hunley was using. A particular given account referenced depended on location and date in question for the most part. Many folks saw different things at different times. Hunley did lots of trials, testing and practice runs both while still in Mobile, and later in Charleston. The tow behind torpedo worked well in trials in Mobile. In Charleston with the currents was a bit tricky, especially when you have to try to manouver around other friendly ships to get out, made it a bit more risky with that thing bobbling along on a small skid around 150 feet or more behind you. Direct contact torpedo had its inherited risks as well. Based on eye witnessed accounts that saw the vessel on Feb 14th and the morning of Feb 17th, it would imply the spar mounted but release & trip cord detonated type was most likely in use on its final mission. Given accounts refer to this given torpedo being about 135 lbs.

The Attack
....on the night of February 17th. About 8:45 P.M. I saw something in the water, which at first looked to me like a porpoise, coming to the surface to blow. It was about 75 to 100 yards from us on our starboard beam.......At that moment I called the Quartermaster's attention to it asking him if he saw anything; he looked at it through his glass, and said he saw nothing but a tide ripple in the water. Looking again within an instant I saw it was coming toward the ship very fast. I gave orders to beat to quarters slip the chain and back the engine, the orders being executed immediately [Housatonic; Officer of the Deck; Acting Master John Crosby]

....I then saw something resembling a plank moving towards the ship.... it came close alongside, a little forward of the mizzen mast on the starboard side. It then stopped, and appeared to move off slowly.....took the rifle from the lookout on the horse block on the starboard quarter, and fired at this object. It had the appearance of a plank sharp at both ends; it was entirely on awash with the water. [Housatonic, Lieut F.Higginson]

....On reaching the deck I heard for the first time it was a torpedo, I repeated the order to slip, and gave the order to go astern, and to open fire..... I hastily examined the torpedo; it was shaped like a large whale boat, about two feet, more or less, under water; its position was at right angles to the ship, bow on, and the bow within two or three feet of the ship's side, about abreast of the mizzenmanst, and I supposed it was then fixing the torpedo on. I saw two projections or knobs about one third of the way from the bows..... [Housatonic; Captain Charles Pickering]

Torpedo weight-release / Ballast
I havent seen any original period notations regarding concerns over potential stability issues after releasing the torpedo. The Hunley was quite heavy for its small size. I wouldnt expect that taking off about 135 lbs would have rendered it unstable. They had a fore and aft water ballast tank for submerge and surfacing, which could be adjusted independently to level fore-aft. (Operator error with this is what killed the second crew.) The side fins when in motion could also be used to adjust pitch. The Hunley also had about two tons worth of external iron ballast plates mounted underneath the vessel attached by T bolts that could be released from the inside.

Blue Light Signal
... a recognition signal using a blue light was arranged between Dixon and the men of Battery Marshall for the purpose of guiding the boat back to port after dark [witnessed account of the exchange by Corp McClarin, 23rd SC Infantry whom was detailed to assist Lt Dixon make some adjustments to the Hunley on the morning of Feb 17th]

....The day of the night the perilous undertaking was accomplished, The officer in command [Dixon] told Lieutenant-Colonel Dantzler [in command of Battery Marshall] when they bid each other good-by, that if he came off safe he would show two blue lights [J.N.Cardozo, Charleston 1866]

Frederick