I don't have a lot of experience with boots for off-road riding but I do have a lot of experience fighting to find ski boots and shoes in general that provide the width and volume I need in the mid foot. I tried the Sidi Xfire with the Goodyear welt hoping the width would work, but they just didn't have the volume.
More than anything thank you to Brian who spent 10 minutes on the phone with me just to figure out exactly what the issue might be and recommended the SG-22 specifically for the molded toe box.
The SG probably could have sized down as their EU to US conversion is larger than Sidi, but the volume definitely didn't come from the size alone.