If you are making a "perfect 45 degree" rolling offset, then the 2-hole would be a 45...If not...You will have to use Trigonometry instead of the Pythagorean Formula. My "good ol' boy method" and advice would be to set it up in real world, installed configuration. If necessary, bridge tack some dummy pipe extensions on and secure it down with a "V" head clamp (jackstand vise) This usually come out to be faster than struggling with the complexed math and resultant errors. Along this same train of thought, when my figures have been questioned, I often find a wall and mark reference lines on the floor and vertical wall to double check the math. It may not be the most professional looking approach, but beats the heck out of cutting it apart when you use cosine instead of cosecant