Once again, an early middle ages topic..
From what I understand, the larger round shields covered about as much area as a kite shield, referencing the larger round shields used in shieldwalls. I would think both should be in the "large shield" category.
But the Kite shield's advantage was to provide better coverage for the legs. I wonder if a good way to represent a kite shield would be to not apply the +1 to legs if defender has a shield when swinging.
What is also kind of interesting along a similar line is that the time period where the kite shield was slowly replaced by the heater shield is also the same time leg armour became commonplace. This ties in well with the idea above.
In my gaming group, kite shields do protect the legs, we simply cancel that +1CP you are talking about.
http://fflr.dk/tabletop/TROS/Armour.pdf