I calibrate and generally the calibrated speed is a few mph under my current speed. As long as the altitude is good, I then manage the throttle.
Here is what I do:
1. At the dar ring, open doors, this slow you down a few mph.
2. Begin calibrating at three second intervals.
3. When alt is matched, stop calibrating
4. Reduce throttle to match calibrated speed. It does not take much.
I have also found that flying a +7 boost works great for speed, endurance, and bombing accuracy.IIRC I was rolling 350 or so at that setting yesterday once I lost the wing bombs.