According to the IMPBA rulebook:
Belly pans are allowed but must terminate aft smoothly and extend no further than 50% of the aft plane. Belly pans must be at least 3/8 inch above the bottom planning surface of the boat measured with the boat resting on its 3 points on a static table.
To me, this says:
1) The belly pan must end before it goes past the middle point of the afterplane or half way between the sponson transoms and the rear of the hull.
2) A belly pan must be at least 3/8" above the bottom planning surface. The question is are they referring to the sponson runners or is the aft bottom panel considered a planning surface?
IF I am interpreting the rule correctly, that has me thinking the pan is too long. That being said, I would hope someone more familiar with the IMPBA rulebook would chime in on this one