Thanks-glad you like what I've done so far
I hope the end result comes out well. It seems to be going okay. Some of it's a bit wobbly (my skill at cutting plasticard could stand some improvement), but overall I think it'll be acceptable when it's done 
Looking back over my initial reply, I realize you misunderstood me just a bit.
Oh, yes, the T-Rex-mobile is utter madness incarnate. But the soldiers are a glorious whole, though I did stop to admire the 'flamers' a bit. However, it was the idea of taking this to a 40K table that, indeed, clinched my speechlessness. Hear hear!
'Cavorite gravity engine'-which reduces the weight of the machine by 90%-allowing the T-rex to be able to carry it 
That makes sense.
But how do they steer?
Will there be a stick with a goat on it hanging in front of Rex's face? Or a skull cap with electrodes?
What make is Rex?
Well, he did say something about 'and may add a chain leading to the dino's mouth-'; however, I also admire your suggestion of carrot, er, goat-and-stick. 'S'uh, the shot carried away the steering mechanism! Goat's still in the air!'
As for the Cavorite engine, obviously a tired, old cast off from the Aerial Naval unit. Insufficient to carry a whole 'nef.
Doug