So this has probably been discussed before and if so I'm sorry. But here goes... From the pics I've seen It looks like Hound's alt mode is huge. Quite a bit bigger than Optimus's. Is that correct? I mean even taking into account that Hound is 'fat' (and I love it! God he was so awesome!) it seems like they were probably doing some mass shifting cheating on him. Also Galvatron's alt mode seems like it would be much smaller than Prime' yet his robot form still looked bigger to me. Thoughts?
No, it's not bigger. It's just a 3 axle military transport vehicle. It'd be significantly shorter in length, and the cab portion wouldn't be quite as high as Optimus' either. Hound's alt-mode would be about the same size as Optimus' flat-nose incarnation (which is much smaller than his new reformatted mode), and while the rear of it has bodywork, it's almost entirely hollow because it's for holding troops. So he's a bit smaller, plus he's short and squat. No cheating needed.
Ah, I keep forgetting that they didn't use the troop transport version. Same vehicle and size though. Refueler, in that configuration, methinks? There's SO many versions of that truck....transport, fueler, fire-engine, towing, plow, etc
There may not be mass shifting in the strictest sense (plus I've always found 'mass' a bad choice of word as two things of different sizes can have the same mass if they also have different densities), but there's always been a little bit of what could be called 'comparative size massaging' going on in the movies. I think it was most obvious with Optimus turning into his evasion truck mode, but I'm sure it can be forgiven