I had in front of the SS, the size 36/38, in the SS I wear now 40 and I've (equivalent Gr. 42/44) the BabyBelt in M ordered. The velcro fits and has thus still much room for the last few months and the growing belly.
To "long-term use" I can not say much. The abdomen is well supported. I felt that immediately. I wonder if the belt also alleviates the drawing in the pelvic region.
For orientation: XS = 36; S = 38/40; M = 42/44; L = 46/48; XL = 50/52
Update: After nearly a month-long gestation period, I can say that pulling in the groin area is almost entirely disappeared. The back pain is not completely gone. But are clearly better and more bearable. I had to make it even bigger. Now the belly is growing with so vigorously. But still fits very well. For me, the purchase was worth.
Update 2: Now that I have to ask the BabyBelt getting bigger, I have found that the Velcro rubbing against the skin. Carrying the BabyBelt now about the maternity trousers.