PMDG 777/747F varients GSX won't load cargo into Main Cargo Deck

Hi everyone

I've just purchased GSX and it's an amazing product. However, when I press "Request Boarding" for the PMDG 777F it sends two smaller cargo loaders to the right cargo doors. In this instance, I want a larger cargo loader on the Main Deck Cargo door. I know GSX can only support two Cargo loaders and I've tried playing around with the config; this problem also occurs with the PMDG 747F too. I have selected a 90% payload which is apparently enough to enable the Main Cargo Door loader. 

Any replies I am grateful

Thanks 

Jack