Obviously DXA sucks.
Get a pair of calipers. Track your skinfolds in a few places. That and measuring the circumference of your body in strategic places will tell you if you are getting bigger or smaller.
Just track the skinfolds, no need to bust out the formula.
Also, the best thing for your purpose is your eye or the eye of someone else. You are looking for a cosmetic appearance that is pleasing to you and others. Using the right metrics (i.e. visual aesthetics) is more important than having some arbitrary numbers.