Position of the player's arm in 1st person, from Survival Test

By Goodlyay, found by looking at the source code for ClassiCube.

Note that while the arm is on the right side, it actually uses the model of the left arm. (This wasn't noticable since your arm was always steve, but since there are custom skins in ClassicalSharp, we will use the proper right arm.)

Rotation origin of arm is same as on the player model, as far as I know.

The arm model is scaled by X 1, Y -1, Z -1
The arm model is moved by Y + 0.2
The arm model is rotated on the Z axis by -120
(This next part wasn't in the original, but fixes weird UV mapping on the skin that was unnoticable in the original due to steve's texture.)
The arm model is rotated on the Y axis by -90