I'm a bit busy so I don't have time to check further, but the formula for the base power of Gen 2's Hidden Power, as given by
http://www.psypokes.com/gsc/dvguide.php and
http://bulbapedia.bulbagarden.net/wiki/Hidden_Power_%28move%29/Calculation is incorrect.
The pages there say:
HP_Power=(5*(v+2w+4x+8y)+Z)/2 + 31
where
* v is 1 if SpcIV>=8; otherwise 0,
* w is 1 if SpeIV>=8; otherwise 0,
* x is 1 if DefIV>=8; otherwise 0,
* y is 1 if AtkIV>=8; otherwise 0,
* Z=3 if SpcIV>=3; otherwise Z=SpcIV.
However, I have verified that it is possible for SpcIV=11 to have a higher max damage than SpcIV=12, 13, or 14, assuming all other IVs are the same and all other circumstances equal. So the above formula is incorrect. If anyone can verify the actual formula, that would be welcome.
(I swear I remember somewhere 6 years ago where it said that Z=SpcIV mod 4.)