I'm planning picture frame moulding below a chair rail in the dining room. The chair rail, picture frame, baseboard and walls will all be painted high gloss white to give the appearance of raised panel moulding. One wall has a heating return grate 18" below the chair rail to just above the baseboard. I'm planning two picture frames on this wall. Should I make these picture frames shorter than the rest so that I can make complete squares, or should I make these frames the same length as the rest and just stop the moulding where it meets the grate?