I think currently the plane can only hold two of these modified PL-12s in each bay, but comparing it with pictures of F-22 with a full bay of three hard points vs one or two, I think J-20 can also fit three hard points internally to make six missiles overall.
The current situation may reflect missile tech limitations or this missile being a stop gap. looking at the bay with only two hard points, it appears to be very roomy almost like they aren't even trying to squeeze and make use of the space.
I don't think they'll be stacking missiles, even if it is quite deep. The depth may be to accommodate A2G weapons or larger diameter A2A weapons. Stacking missiles is much too risky.
The current situation may reflect missile tech limitations or this missile being a stop gap. looking at the bay with only two hard points, it appears to be very roomy almost like they aren't even trying to squeeze and make use of the space.
I don't think they'll be stacking missiles, even if it is quite deep. The depth may be to accommodate A2G weapons or larger diameter A2A weapons. Stacking missiles is much too risky.