Here ya go Rick.
If you want a surefire way of countering a direct SDR, use your own SDR, what either happens is the two clank, or you both get hit out of your SDRs.
I HATE ditto matches, the only reason I would say otherwise is because the other Sonic plays a fast-paced style.
You can't mindgame or be affected by mindgames if you know your own character (in this case, Sonic), because you should know what your own character is capable of and their own weaknesses to exploit, but the stupid thing is your opponent is essentially you and they will know that they have to mask their weaknesses. God I'm not even sure if I'm explaining this right!
It should be very hard to land hits, because both opponents are at the peak of their game, and they should know what part of certain moves connect and what their purpose is, so you can't be using the same moves you would use universally like you would in some other matches. Take for example Hyphened-USmashes... you should know how long you have to shield that move, and when to take advantage of Sonic's dead frames... however why would your opponent want to use this attack if he knows to expect you to fully shield his attack? He might just do something entirely different, which is at the same time discouraged because your opponent knows counters... and sometimes even counters to counters! Nothing is guaranteed in a ditto matchup, and nobody wants to make an attack because every move you make will put you at the disadvantegeous position!
Edit: we're on page 300... Dis... Iz... METAGAME!!!!!!!