I've cold set 4 frames, all Columbus tubing. I haven't broken a bridge yet. I tried the threaded rod method on a TSX frame . Every time I spread it with the rod, the frame just went back to 126 mm when the rod was removed. I probably got it up to 145 mm with the rod and left it for a day, It just went back to 126 mm. I use the 2 x 4 method, but slightly different than what is seen on the web. I lay the frame on a blanket, put the 2 x 4 under the top drop out and against the bottom chain stay as close the the bridge as it can go ( if you cut the end of the 2 x4 at an angle, you can get it right up against the bridge). I hold the bottom drop out down with my foot and lift the 2 x 4. It doesn't take much to cold set. I then flip the frame and do the other side. I constantly check alignment with the string method and work both sides gradually. Then I check the dropout alignment and derailleur hanger alignment.