NicheStack TCP/IP Stack

Has anyone evaluated the new NicheStack provided with 6.1? I'd like to know what the achievable bandwidth and whether it lends itself to being stand alone. I suspect the MicroCOS is slowing down the maximum throughput, but that's just a guess from what I've learned using the lwIP stack.

Further, I have only been able to attain a max throughput of approx 50Mbps using the stand alone lwIP with the following configuration:

NOIS II/f uController

100MHz sys_clk (I can get a little more bandwidth with 125MHz, but any higher results in dropped packets. I'm a little skeptical of the reliability at rates higher than 100MHz due to the timing analysis warnings reported at compile time)

LAN91C111

4k tightly coupled instruction memory, 16k tightly coupled data memory (not sure if this has any real effect)

Optimized code and system library (-o3)

1024 byte packets over UDP (continuous loop, repeating the same data)

With the above configuration I get a solid (no packet loss) 6000 packets/sec, which amounts to roughly 50Mbps. My target bandwidth is 60Mbps, and I've read others here achieving 80Mbps. Does anyone know what I am missing?

Thanks!