On most open water training dives the students and staff will spend a lot of time vertically on the surface talking and getting ready to descend and then again reviewing the dive between skill sessions and the experiential portion of the dive. This is not normal diving. On a typical dive, you should spend very little time in a vertical position. Trying to trim your weight so that it is easier to achieve a vertical orientation will only cause you to compromise your trim in the horizontal position that is the position that you want to achieve both under water and while swimming on the surface.
As others have pointed out, you can solve your problem by inflating your BC only as much as needed to keep your head out of the water. Trim your weight for your underwater horizontal swimming position.
As others have pointed out, you can solve your problem by inflating your BC only as much as needed to keep your head out of the water. Trim your weight for your underwater horizontal swimming position.