Re-writing Reports for Upgrades

I am seeing lots of errors being logged in my Event Viewer after my upgrade to 10.2.600 related to SSRS, but all my reports are (theoretically) running fine. I think it’s related to AR Invoice, but the world may never know.
Prior to the upgrade, I did trim down the AR Invoice RDD (a customized copy of the base) to make it work with this version, but alas.

So beginning down the road of re-writing a report to fix upgrade issues, what are the proper steps to do so?

I started by creating a copy of the base ARForm RDD. Then, I plan to bring in the custom linkages that are needed and then tie this RDD back to the custom report style.
Is this the right way to do it? And how should one make sure they are doing this as efficiently as possible to ensure we aren’t bumping up against the exceeded columns limits that SSRS has?