there are three types of grill connections that I have seen on sunn cabinets. one is where there are screws on the front holding them on, two is where there are little locking plastic parts that snap on to the grill, and the third is where the grill is stapled to the baffle board and you have to take it off and remove it that way.
on my 68 solarus 2x12 it's stapled, and just on the 2x12 alone the board is attached by 24 screws and held on by at least twice as many staples, so I shudder just thinking of what the 2x15 would look like if it is attached this way