The phrase "are even more solidly" is correct and usable in written English.
It can be used to emphasize a stronger degree of certainty or stability in a comparison or assertion.
Example: "The new data suggests that our conclusions are even more solidly supported than we initially thought."
Alternatives: "are even more firmly" or "are even more securely".
The Northern Sea Route is a centuries-old dream comparable to that of the Northwest Passage of Canada, which is even more solidly frozen.
One photograph from the Apollo days is even more solidly embedded in our culture than that of a triumphant Aldrin; it is the image of Earth from space — looking, as Armstrong would say, big, and bright, and beautiful.
"The way I played on Friday was disappointing and I think I'm even more disappointed today". Lee Westwood "played solidly" to card a 70 and be in contention at two under.
Asked what they hoped to accomplish by lobbying a solidly anti-abortion lawmaker to be even more anti-abortion, Cascio said, "Well, she's not voting pro-life".
"[Earthlink and Mindspring] are now even more solidly entrenched in the ISP space," says Klein. "What AOL has is content and is a quasi-portal," says Takata.
The bank bailouts, loan guarantees, and government-initiated mergers were introduced without enough strings attached, and they bequeathed us a system in which the too-big-to-fail problem is, arguably, even more solidly entrenched than it was previously.
You could dismiss the device as a literary trick — Pynchon for beginners — if the stories weren't bound even more solidly by theme.
Cemented there even more solidly is the memory of a day in 1967 when, after a practice session, Hogan "decided to reveal to me his mysterious 'swing secret.' The one many thought he never told anyone.
There's also an optional over-the-ear hook to keep the thing even more solidly in place.
