Click on my screenname and read my previous posts regarding aneurysms and ARBs/ACE inhibitor drugs.
I believe your doctor's advice is sound. I had an ascending aortic aneurysm repair last November. When the surgeon repaired it, he said it measured 5.8 cm. The preop testing showed it to be approx 5.2 - 5.3. They usually wait until it reaches around 5.5 cm, depending upon some other variables. You low blood pressure is a big asset in this case. It should keep it from enlarging for a good while.