Everything depends on whether you are going to have an upper floor on the garage. The "byglarna" or as they are called: the baskets can be placed with c/c 40 cm, and if you have 4 "tolvor" in 2 planes, I think that should be more than sufficient. To be safe, call Ytong and ask what they think about that reinforcement. I assume you will cast an unbroken full-length beam for both doors.