I've marked this for the PM to review.
Not sure I understand your question... I have seen other customers use shadow routers next to the production routers for which they are interested in creating IP SLA operations. They use the shadow routers specifically for sending IP SLA traffic so the tests don't interfere with the traffic or performance on the production box.
Shadow routers should be deployed as close to the performance measurement point as possible. They are not connected between routers but rather attached to a production router to off load the IP SLA overhead from the production router. For HSPA emulation use a G.729a Codec.
shadow router.jpg 21.7 KB