I agree with the suggestion to send it via courier. The closet space in the plane is limited, really, and there would be no assurance that the FAs can fit it in there, or that there would be no damage. As also suggested, you can try asking the SG office. QR is not famous for their quick and efficient ground service, but I find that the SG branch gives quicker and more concrete replies (as opposed to Doha or Paris offices).