That is what I would do. FWIW the hole pattern is going to be a rectangle with each side some multiple of 100mm. And the holes don't have to be all that precisely located if they are a little bigger than the bolts that will go through them. The bolts are metric, M4, M5 or M6 IIRC. I don't recall the pitch. Choose a length that goes well into the threads but doesn't bottom out when tightened.