Nice tool, thanks a lot.
I am using it slightly differently, I have only 2 ad locations I want to show rotating banners, a 235x60 in the header and a 468x60 in the footer.
I use the standard Horizontal placeholder "@vbbanners@" for any header ads, and the "@vbbanners_vertical@" for any footer ads, ticking "vertical" in the ad set-up, even though the ads are not vertical it seems to work.
Cool :-)
www.acorndomains.co.uk