In From Narnia to a Space Odyssey: The War of Letters Between Arthur C. Clarke and C. S. Lewis, the first very short letter from Lewis to Clarke (December 7, 1943), Lewis is responding to Clarke's accusation that Lewis sees all SF as trashy space opera and that Lewis' portrait of Weston is colored by that. Lewis responds:
I don't of course think that at any moment many scientists are hidding Westons: but I do think (hang it all, I live among scientists!) that a point of view not unlike Weston's is on the way. Look at Stapledon (Star gazer ends in sheer devil worship), Haldane's Rosetta Worlds and Waddington's Science & Ethics. I agree Technology is per se neutral: but a race devoted to the increase of it own forces & technology with complete indifference to either does seem to me a cancer in the universe.
(From Narnia to a Space Odyssey, p. 40; errors in original)
In a quick skim of the book, I don't see another reference, but I'll go back over it in more detail and add anything relevant.