"further opinions" is correct and usable in written English.
You can use it when you want to add some additional information or when you are looking for further opinions on a matter. For example: "We have already received many opinions on the matter, but we are looking for further opinions before making a decision."
However, the second doctor agreed surgery was required – whereupon his mother, Sally, demanded further opinions.
The more the opinion formers form opinions about Eton, the more they consign themselves to having to form further opinions about Eton.
Instructors can consider discrepancies, share the rubric and results with faculty colleagues for further opinions, and revise the rubric for use in class.
We've done that bit (although of course, further opinions are very welcome) and, more to the point, we have something new and exciting and intriguingly difficult to discuss: Boneland.
And when "Aquaman" director James Wan tweeted his appreciation of the trailer, his use of "live action" spurred further opinions about just what to call Disney's latest re-creation of an iconic property from its gilded vault.
He added, "To avoid further damage to the economy, the N.L.R.B. must take the responsible course and cease issuing any further opinions until a constitutionally sound quorum can be established".
No further opinion poll results [are] published or broadcast after February 20.
If nothing else, the Nets' decision saves the world from further opinion pieces about Collins's continued unemployment.
MR. JUSTICE MILLER delivered, at a subsequent day of the term, the further opinion of the court.
Taney's further opinion that Congress had no power to exclude slavery from the territories and that Negroes could not become citizens was bitterly attacked in the Northern press.
Capello and his players landed at Heathrow this morning but were whisked away without offering any further opinion on Sunday's shattering 4-1 defeat by Germany in Bloemfontein that consigned them to an early flight home.
