Cisco DS3 performance specifications

To any and all in earshot,

I am engaged in setting up a sytems level test lab for the purposes of
among other items, DS3 performance and interoperability between Cisco 12000
and several new and emerging edge switch devices.

In order to set a baseline for performance expectations, I am attempting to
historical data on earlier testing.

The nasty rumor I am hearing is that Cisco DS3 interfaces at best deliver 50
- 60 % throughput.
This is supposedly attributed to the way they apply their Traffic Shaping
and Policing at the port level.

I need to obtain documentation that either validates this, or presents the
correct information.

Many of the edge devices involved in the testing, support high levels of
even at the channelized subrate. An increased need to buffer the data, to
for a potential mismatch in bandwidth capabilities, would just add to the
and sour the testing.

Any and all information is valued and appreciated.