What i gained from this thread is " (d) I put a large rectangle (4 ads) at the foot of the page, blended and matched." will try it.
From what I learnt from watching an adsense video the top earning ads are the first ones showing, therefore at the top of the page not down at the bottom. If clicked they will indeed take away from your top value ads.
There is very good reason not to. Google puts the highest-paying ads in the first spot in the first block, with ads becoming less-paying as you traverse down the page. If you display less ads, chances are that people dont see the low-paying ones and go for a higher-paying one instead. Although your total click count may fall, for many the eCPM will actually rise.
Thanks for the great tips! I was gonna say Ef You! but decided that it would probably run contrary to this site's politeness policy! Why don't you go take your nastiness somewhere else!? D.