I enlarged my opening to 19' and framed for 2- 9' wide doors. You would be surprised how much difference a 9 foot door makes compared to 8 so a 10 foot opening would be dramatic. A 4x4 post sandwiched with 2x4s to support the middle of the header and sistered 2x4 studs as posts at the sides. One door with an electric opener and one dead bolted door I manually push up (the only doors into the shop). If my power goes out I can always get in and the manual door is much faster than the electric opener.