A little bit of slack on the non-tensioned side is okay... see "Ackerman effect". IOW, no need for an off-set bellcrank, etc.

The problem you're thinking about, which is endemic to many of these "tweener" size models, is that the cables will rub/drag against the rear fuselage former unless you remove some wood for clearance. I know its a LOT of data to plow through, but this was covered, with good photos, in the H9 Extra thread; perhaps midway through?

Crossing the cables helps, but they will still rub unless you remove some former wood or run the cables though plastic sleeves back there. Also, if you cross the cables you will have to insulate them from each other, by fixing a sheath of some sort (I used a piece of inner NyRod) where they cross. Otherwise, they will eventually rub through the plastic coating and you'll have metal-on metal... and that's bad juju.

The plastic tube trick around the former is the quick fix, but still causes drag and uneven tension. There is plenty of room to cut a hole in the covering on the bottom of the fuselage, get your Dremel up in there, and hog out that former. A patch of U-Cote seals the hole. The only drawback to THAT method is that a roll of Pearl Blue UltraCote is close to twenty bucks. Any color of U-Cote will do, for sealing purposes.