Chapters 4 & 5 are possible at lower levels - just don't expect an easy ride. The main problem with leaving lots of side quests until chapter 6 is that by then they are just too darn easy.
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Time is an illusion. Lunchtime doubly so.
Epona of The Laughing Hyenas
Proud winner of the 'Most Useless Post 250 Has Ever Seen' Award 2001. "I'd just like to thank my friends and family, without whom none of this would have been possible..."