7/10 sounds a bit... generous? It's so double-edged that it's just not worth the room. The usual +10/20/30 are usually enough already with DP's high attack power you really don't need to waste a stadium to make it x2 for both you and opponent.
I'm saying only 5/10... It's so pointless unless you're specializing Lv X Pokemon who has x2 weakness, then I'll say 8/10 for those specified decks.