Well, so I to have do some 'bad' thing (looking into his ROM).
Check 0x80005E8 in his hack and you will find a hook. It seems that he has rewrite the "tile behavior check system" so he wrote his routines at 0x6XXXX (That's the location of the tilebehavior check function in original FR ROM). You should write them to some free offset, absolutely. If everything goes smoothly, that's all. His script is at 0x803B79, which can be seen in XSE. It may be integrated with some parts of his routine, so some part of the routine may be useless for your script so you should know what he is doing here haha.