Okay, angle on bow is largely a matter of practice, the better your 3D perception, the better you'll do, (in case you don't understand what it is, imagine you are stood on the bridge of your target ship - however far you had to turn your head either to port or starboard in order to see the sub's scope is the angle on bow) Firing a spread with one either side of your dead centre shot will help to minimise calculation errors if working out AOB is not your strong point.
You could try emulating what some sub skippers used to do to get better at it. They would put a model ship on a piece of card with a protractor underneath it, and have someone turn it to an angle, then they'd look at it from a few feet away through the wrong end of a pair of binoculars and try and guess the angle. This is not as stupid as it seems, I used a similar method when learning to fly, by putting a book on the floor of a big room and standing at various distances to get familiar with glide slope angle sight pictures. Practical stuff like that really works well.
The stadimeter image needs to be placed with the image's waterline sat on the tops of the masts on the real image of the ship. This is tricky as in real life (and the sim) these are pretty thin at long range, and were/are often painted a pale colour at the very top to make the the mast look shorter - exactly to screw up range estimates, so look carefully.
In real life, the stadimeter was designed to be used at the high magnification setting on the attack scope, and would be incorrect (without a calculation) if used on low magnification although I'm not sure if this is modeled in SH4, and it may work in both modes although high magnification is the better choice (and the correct one if you are trying to do it like they really did.
At extremely long ranges, the waterline could actually be below the horizon, so watch out for that too.
Speed is the one where you really do need to go to the plotting map to get a good estimate of two timed bearings (with range estimates) which can then be plotted on the map joined by a line and multiplied (depending on how long you timed it) to get a speed in knots. But if you want a quick way to do it, I find that you can get a reasonably decent estimate from the bow wave and a bit of experience, fire a decent spread and this will more often than not result in a hit or two. To do this you'll have to manually set the TDC on the torpedo settings screen.
One other method is to take an AOB guess and then turn on the position keeper and keep watching the target, if the position keeper seems to constantly match your sight picture, there's a good chance your speed estimate is correct.
Whatever methods you choose, don't forget to update the TDC. Good hunting
