Hi Paul - that is correct, you just need to finish - ChangeDegree to at least 2 but I used 3 in the U direction on the exploded surfaces - see my example file above. - oh - OK - I see - the ribs are all the same so Loft makes a single surface in U. Hold on a bit.
@Paul_Adams - in this case it will work out better if you first
Rebuild the curves (degree3, 4 points should work) because they are made of two tangent segments which lets the loft explode in the long direction. Or use the Rebuild setting in Loft.
Since the curves make one straight section in this case,
Split the result with the input curves and
ShrinkTrimmedSrf on these then carry on as I suggested -
Elevator Ridge Test_PG.3dm (747.2 KB)