The phrase "are rather massive" is correct and usable in written English.
It can be used to describe something that is large in size or extent, often in a comparative or subjective manner.
Example: "The boulders in the canyon are rather massive, making it difficult for hikers to navigate the area."
Alternatives: "are quite large" or "are fairly substantial".
These are rather massive headgear that, when twinned with mirrored goggles and the pounding beats of artists like Lil Wayne and Cash Money Millionaires, shut out all outside stimuli in the pursuit of perfect prerace concentration.
"Weddings are rather massive events.
In summary, since operational RNA macromolecules are rather massive in numbers and diverse in functions, our efforts to understand them have to be significant enough.
Massive lesions are rather large objects to be detected, but they show up with a faint contrast slowly increasing with time.
It is rather a massive breakage of atomic bonds diffused in a volume of characteristic size.
In criticism of Searle's response to the Brain Simulator Reply, Kurzweil says: "So if we scale up Searle's Chinese Room to be the rather massive 'room' it needs to be, who's to say that the entire system of a hundred trillion people simulating a Chinese Brain that knows Chinese isn't conscious?
The reason I want to highlight this is because it has turned out to be something rather massive.
It's a brilliant opening to the Other stage's bill – even if the "secret" element of their appearance was rather ruined by a massive Beady Eye banner that had been draped across the stage.
The generally very large size of conifer genomes is rather a result from massive invasion of transposable elements early in the history of the group [ 31].
It was massive then – it was rather like the X Factor going round the country then.
It's lovely to see politicians come out with clear ideas and policy, but Ed Miliband's idea here is so massive that it is rather terrifying.
