If you are near the ToB cap, it'll lack a few high level spells, but will still have level 9 spells.I don't think that a simulcrum doubles your spells. The simulcrum comes in several levels lower and lacks your highest level spells.
'Best Mage' Justification
[url="http://www.sorcerers.net/Games/BG2/SpellsReference/Main.htm"]Baldur's Gate 2 Spells Reference[/url]: Strategy, tips, tricks, bugs, cheese and corrections to the manual.