The 2018 must have a bigger upper body and arms than the 1978, because it was an even harder struggle getting the Hot Toys Luke Jedi padded suit onto it, than it was when I tried it on the '78.
Barely managed to get it over the shoulders, but had to remove the foam pads that were stuck to the shoulder straps.
As with the '78 I filled the boots to the top with 'Power Tack', then plugged the the ankle pegs into them until the figure's height matched that of the '78.
With so many actors of varying heights playing Michael I wanted to settle on a single stature to represent 'The Shape', so that the figures would match.
I went for the taller option, and tried for James Jude Courtney. It's a balancing act due to the length of the overalls.
Not easy to measure accurately, since he's wearing a mask, but he works out at about 6' 2 1/2" above his boot soles to where the top of his head would be inside the mask.
Still really difficult to photograph without proper lighting conditions:
Comparison to a more regular height figure (who's a bit on the short side):