You have tons of room to do whatever the hell you want,
I would not go straight up because then you will have to get a rain cap and that will distort the flow - you want to "jet" the fumes as far away as possible and that way they will get defused if the wind happens to bring some back at you.
The solution would be to come off the side and head to the front and then direct it down and slightly left at approximately a 45 degree angle --- your doing two things that will help --- your getting it far away for proper dissipation whilst changing the height level away from your shnoze...
You use the length of the front of the vehicle to get further out without impeding its turning radius, you then put a 45 degree elbow at the end with a small nipple for directional purposes... what's not to like?
Don't want to run open header? throw a muffler inbetween, plenty of room.