Question about criteria to validate a system

[Gilles4Fun]

Hello, Sorry for my English, I'm from Belgium and I speak French every day, not English ;) I'm trying to find a football system, I've potentially found a window but I've a question : Is the edge (My Odd / Book Odd) a good criteria to extract a profitable window from a system ? In fact the system is not profitable if the edge is under 1.20 and profitable over. The book odds are the avegrage odds from football-data's files (I only bet on favorite home teams) I don't like very much this criteria because it's too relative : If I take the best odds, this edge will be smaller and I'll have more bets to place with the same system and a very probably different record. What do you think about this ? Is a Edge > 1.20 realisitc ? Is it possible to found a window where my odds would be better than 20% over bookmakers prices ? Thanks for your replies !