Surface area is what's important to calculate how many fish you shouls add. In a well filtered tank, as a generous measure i would say...
24x12=228 square inches of surface area, each 1" of fish needs 10 square inches of surface area, so you can have 28 fish 1" long, (or any combo of reasonable sized fish up to the max - this however doesn't allow for growth!)
If you currently have 11 corys at 1 or 2 " that would be 22 " out of your 28" allowance so 6" of spare space, so 3 x albino pandas should be ok - i would stretch this to the 4 or 5 you wanted

- the body sizes do not include tail, so you should be ok but that'll be your limit really.
Obviously when fully stocked you always need to follow a good water quality regime & keep a close eye on everything.
The only problem then would be when you next see some cute little new cory species & have no room

- time for another tank
