http health monitor on LTM issue with IIS7

Hi all, sorry if this is the wrong forum, but i was wondering if anybody has any creative solutions for this. We have multple web sites in IIS7 that are not using host headers, they are actually bound to different IP addresses. We were trying to test failover of our pool nodes, by stopping a web site in IIS. (all other IIS web sites are still running, we just stopped one.) The problem is, it seems that in IIS if at least one web site is running, the server is listening on port 80 on all the IP's that are bound to sites. So by just stopping the web site and leaving the others running, the f5 is still getting an http health monitor response. (it's a 404 error, but the server is still listening). So I was wondering if anybody has any thoughts on how to handle this. We were thinking of making a more granular health check that looks for certain web page responses, but all of our sites are different and that would require a lot of configuration. Does anybody have any other ideas?