Spinal Hub

Recently I booked a flight from Darwin to Melbourne. I spoke to Virgin special services prior to booking and they advised me to book the flight and then get back to them with the wheelchair details. When I did this I was advised that the max weight was 120kg, which I think would rule out most power wheelchairs. I have flown Qantas and Jet Star with no issues. They said the reason was OH&S considerations despite me telling about Qantas and Jet Star.
Have other people found this? Or have you found a way around it?