Nice solution. Can you loosen one barrel enough to rotate it without moving the other?
Thanks. I didn't notice any major 'crosstalk". Because the slot is cut on the side and the clamping bolt is also a mounting bolt the barrel does move up a bit when the clamp is loosened. It didn't seem to cause major problem. When looking at the FF spot the beam moves a few mrad when loosened. Once the barrel is optimally rotated it returns to position when tightened.
I prefer to have the slot on the top if possible. I built a 4 banger with a similar barrel method almost 2 years ago. No Lie... I haven't had to touch the mounts for realignment yet.