Edit: After some more ring and score runs today, I'll say all stats are legit
Rivals rules were never added to http://www.soniccenter.org/rankings/rules
, only mentioned here and there.
I believe these were the agreed rules:
-Any character may be used
-Only 5 physical attacks are allowed in score runs.
(personally, I think 6 makes more sense due to the hard challenge mode)
-Story, Challenge, and Cup modes are to be used for competition