Since 2011 I play the white side in either Ruy Lopez or the Berlin variation of Ruy Lopez with Nc3 aka Spanish Four Knights.
Spanish Four Knights is a universal system that can be reached via Ruy Lopez Berlin, Three Knights game, Vienna Game, Nimzovich defence, Petroff Defence and Alekhine defence. My statistics vs a local FIDE Master who is an Alekhine expert increased much when I got him out of hes pet defence by playing 2 Nc3.
I have also Scotch Four Knights in my repertour as well but I have never tried it in Correspondence Chess or in any serious game yet. There are a few lines where Scotch Four Knights can transpose to Spanish Four Knights positions that can also be reached via Ruy Lopez.
I played the Berlin variation of Ruy Lopez with Nc3 aka Spanish Four Knights in all of my white games in five Petroff tournaments at ICCF, including in one final tournament. I have also played it in team matches for Team Sweden as well as in over the board team matches for local club. I have also played it in normal tournaments, both over the board and at ICCF.
|2016||WSTT/RD/019 - Russian Defence, C42||4,5/8: +2 =5 -1||3rd place .|
|2017||WSTT/RD/022 - Russian Defence, C42||6/8: +4 =4 -0||1st place .|
|2017||WSTT/RD/023 - Russian Defence, C42||5,5/8: +3 =5 -0||2nd place .|
|2018||WSTT/RD/28 - Russian Defence, C42||4,5/8: +2 =5 -1||I have no games left but the tournament is not completed yet .|
|2018||WSTT/RD/Final 05 - Russian Defence, C42||1/2: +0 =2 -0||I have 6 games left in this 8 game tournament .|