Kurnass loadouts

I am trying to compose a 6+2 loadout on the Kurnass with 6 AIM-9Gs and 2 AIM-7E-2s. The game says it can’t, and I will have to give up both sparrow rails for an AIM-9.
I know this is more than likely to be a reason IRL, but what is the cause of this? I am interested to know.

Belly rails are only for Sparrows.

I think the 2 Pylons for the belly mounted Sidewinders block the back rails of the sparrows.