The level size shouldn't be anything really big. 150x70 sounds like a typical 2vs2 or 3vs3 level size, and it makes a total of 10500 tiles. For example BBLair has got a size of 128x66 and is already slightly too big for duels, although the gameplay helps there(2 carrots and warps as shortcuts.) I would suggest not to exceed the limit of 8000 tiles total. That way your level should end up small enough, depending on how open it will be. Most importantly, don't divide the level into floors in a similar way like Security Breach v2(which is much more a level for teamgames anyway), as that gives players chance to freeze a game entirely.