Is it better to have 1 adsense unit in the navbar and 2 in the footer area or 2 in the navbar area and 1 in the footer?
2 in nav bar and 1 in footer is good in general.Why dont you place one ad in the middle of a post .468*60 ?
IMO... - something up top... whatever fits well... 300x250's are always good if they blend in - 5-ad horizontal linkunit after 1st post of a thread - leaderboard at bottom or - 5-ad horizontal linkunit at top - square ad of some sort after 1st post of thread - leaderboard at bottom ... then find another suitable location for a 3rd ad unit. I managed to squeeze and blend in a 234x60 in my top nav same as DP here.
the best way is to make test by your self...one month for each replacement... the replacement can differ from site to site.. good luck
From my experience, Link ads blended in the postbit, i.e. mixed with the forum posts always gives better return. Square ads in the index page is fine, but in forum pages, they just never seemed to have worked( for me).