Hi jptmedia,

That is usually a good place as long as you are not placing it where people will unintentionally click the ads. If you have drop down menus this could be a problem.

I don't have any drop down menu's so I should be okay.

Your adsense ad placement is one of the best place to put them. that is the place that get most clicks, regardless of the size. whether it's a 336 x 280 or the 728 x 90 banner size. good luck

I have been getting good results with a link unit under my header.

SO have I. I've made $4.00 in the last 5 days from my site after I put adsense under my header.

yes, it is very visible, but remember to make it same theme as your site