venting this way will work, but consider, the exterior appearance of this venting, and if there is ample ventilation to move the exhaust away?
There is that low profile roof exhaust fixture that is only about two iches high and about 10 by 10. Just shoot the exhaust downward. I would install some sort of baffle that would close when not in use to deter squirrels and insects using this for an entrance.
Also, minimize the turns or kinks in the exhaust line so that you have a nice straight flow.