127mm fans will fit easily. In fact they would almost get lost inside. As Mark has suggested keep the ESC. S cool with fans.
I have the same model, twin 120mm Stumax fans. Twin Yep 180 amp ESC. S.
My all up weight is 20.6 kg. Mainly because I chose to use 12s11,000mah per fan.
She handles the weight just fine. Mind you I don't think I would want to dump it.
Chris