Hello, I was with this same problem and I found that this is a limitation of iReport, even if you hide the content by putting an expression on Print When Expression of Page Footer at the time of rendering iReport reserves that space.
How did I solve it? Well I don’t know if it’s the right way, but it was the best way I could find. Come on...
To my PageFooter I set a size of 1px, then instead of putting all the content on that band what I did was create a subreport containing all the content I wanted to appear only on the first page. I put this subreport in my PageFooter also with the size of 1px and ready, worked as I wanted, because? Simple, by default the subreport automatically expands its size according to its content which makes it appear on the first page, as in the others it does not appear and the size you defined of the band and itself subreport was 1px this will be imperceptible to the user.
In my case it worked perfectly, I hope it works for you too.