I finished putting in my steel 2005 shaft today. Weight difference is maybe a 1/3 can of beer.
Did you happen to measure the end to end length on the 05' shaft? The IQ chassis shafts are 1/2" longer overall than the Rush. I think the 05' 900 was the exception. I'm wondering how the 05' long shaft went right into the new Pro Chassis? I have an IQ and Rush round shaft on my work bench. If someone can post up the Pro shaft end to end dimension that would be very useful. The IQ shafts had a SAE bearing with metal seals and the Rush shafts have a cheaper metric bearing with rubber seals. Unless the PRO has an updated part number the metal sealed SAE bearing will not work on metric shaft as the ID of the bearing is different. OD is the same though so the carrier works.
EZ fix once the details are sorted out.