The infinity focus is rarely a problem. You should do something else - shoot a ruler or a target, like a series of small bottles, positioned at 45 to the camera lens, from the shortest practical distance - like 1m. If your focus is spot on, it will be perfect at infinity as well, otherwise you would be well advised to send the camera for adjustment while it is still fully under warranty. Do it yourself horizontal adjustment is however doable, the vertical one on the R3A is impossible without taking off the camera top.