The phrase "a considerable reservation" is correct and usable in written English.
It can be used when expressing a significant doubt or concern about a particular situation or decision.
Example: "While I appreciate the proposal, I have a considerable reservation regarding its feasibility."
Alternatives: "a significant concern" or "a major doubt".
The ASCL general secretary, Brian Lightman, said: "It was with considerable reservation that executive took the decision to accept this agreement.
It set out to be Lambeth's first use of coordinated metric dimensions, a concept about which she had "considerable reservations", but nonetheless gave "a thorough try".
Chris L. seems like a great guy, too, but I have considerable reservations about Chris and Ali as a couple.
He also said Snowden was "prepared in principle to assist a parliamentary enquiry", but noted the whistleblower's "considerable reservations" about speaking to German representatives on Russian soil.
Digby Jones, minister for trade in Gordon Brown's first year as prime minister, and a past head of employers' body the CBI, said he had considerable "reservations" about whether these kinds of deals were appropriate.
He has to win over a much larger share of more reliable Republican primary voters, who will have considerable reservations about Mr. Paul's policies.
She is no less fascinated by the lives of others, and yet she has considerable reservations about the perils of attempting to commit them to paper.
"I have considerable reservations," says archaeologist Paul Mellars of the University of Cambridge in the United Kingdom.
I, and some other economists, expressed considerable reservations about the usefulness of this policy and predicted that it would not help the economy.
The GPs in our study reported considerable reservations regarding antidepressant drugs, felt unskilled to offer other specific treatment modalities (like problem solving treatment) and experienced difficulties in cooperation with specialized mental health care.
