Hi, I am planning to build a pergola that will stand on top of an existing patio. It will be about 2.5x2.5 m. Is it sufficient to screw together two 45x95 beams as posts, one in each corner, and then 45x120 as a frame around? Then I thought of insetting and angling 45x120 beams inside the frame for some sun protection. Is the dimensioning good or should I increase the size of the frame?