My Hirobo Freya 90 swings 710 blades and it will fly about 10 to 15 minutes on a tank of fuel. At that time I am
ready to set it down and take a break. There is a lot of mental work that goes into flying helicopters.

I really can't see a T-rex 450 swinging 710 blades and even then, I would think you might be able to buy stock
large heli blades.

Most manufactures understand that the more fuel you add the more weight you add. The more weight you add
the more power you need to fly that weight, it is a never ending cycle. Manufactures have found aa happy mix
of weight and power and fuel so that the heli fly for around 10 to 15 minutes.

How much experience do you have with helicopters?