Thanks guys, basically, it's what I thought... Nothing official.
Thanks for the details too Fieari, I had already looked at UK's numbers (though I only have version 4, where did you get version 5?).
My problem, though, is the same with the WotC system and UK's system. When you look at the ECL of the creatures, they really don't compare to PC's.
Look at the ECL of great wyrms (UK's system): from 52 for White to 66 for Gold. Are you telling me that a great wyrm White is equal to a level 52 character? If, as was planned, I have a group of three level 55 PC plus a great wyrm White, I don't expect the dragon to add anything useful to the party except being an extra target for the enemies.
Using WotC's system, as outlined in Draconomicon, a great wyrm gold would be the equivalent of a character with a level equal to HD (41) + LA (a young already has +6). A white would be HD (36) + LA (juvenile has +5).
There's no way in either system that you could have a dragon in a party with such rules. I'm not even sure that I should use only HD to compare dragons and PC, especially at epic level. A great wyrm gold has 41HD. If you compare it to a level 41 PC, it is a lot worse. It casts as a level 19 sorcerer, which means that its magic will be mostly useless. Its attack bonus is quite good, but it will be hard pressed to go toe-to-toe with a fighter with its AC 42; though it might have better hit points (I'm not too sure how high the CON score of a level 41 fighter would be).
Well, anyway, if someone has a nice system to make it work, I'd be glad if he could share
