Jim Purbrick's questions

I'm trying to set up IIS as a software load balancer on a Windows Server 2008 R2 box for back ends serving long lived, HTTP streaming requests. Individual curl requests work fine, but when I use httperf to make 10K connections to the IIS box the current requests seem to max out at 2500 for each of the 2 back ends, rather than the 5000 I would expect. Are the other requests being queued? If so is there some way around it? Is there something else I need to change? Should I use a different load balancer?