I actually think your spread right there is pretty nice looking for the time being, helps get light in there and grow the lower buds. Granted, as your buds get further along and put on weight you will need to tie them up or they might snap.
I would just duct tape some string to the top of the cab, it is not really that much weight that would need to be supported. Try and keep your plants from touching the walls as much as possible, I have had issues with leaves up against a wall creating the perfect warm moist environment for rot/mold problems.