The phrase "a small but substantial" is correct and usable in written English.
It can be used to describe something that may be minor in size or quantity but has significant importance or impact.
Example: "The donation was a small but substantial contribution to the charity's efforts, helping them reach their fundraising goal."
Alternatives: "a minor yet significant" or "a little but meaningful".
Pulling a card from my own pack, he pointed out that $3,000 invested over two decades would add a small but substantial chunk to our retirement savings.
After two decades of increasingly sophisticated digital sound recording technology, many purists still prefer analog over digital recordings, and a small but substantial market persists for vinyl records and turntables.
ANMCs provide a small but substantial amount of primary care services in communities served.
We find that individual policies were considered influential in a small but substantial proportion of significant changes made to operations, with disbursement, tax, and regulatory policies seen as the most influential.
The results of our thought experiment – i.e. our estimation that a small but substantial share of the population is likely to be at risk of accessibility poverty – obviously reflect the transport policies and investments enacted over the past decades in most developed countries.
It was a small but substantial "Eureka" moment: I'd been playing Zelda for a couple hours like I'd play a normal console game, and I was vacillating between going to bed and finishing whatever task I was occupied with in the game.
A smaller but substantial proportion of the VRE cases (19%) also met criteria for community association, without other risk factors.
This mutation exhibited a smaller but substantial reduction in the fraction of complexes to 0.61 ± 0.02, relative to wild-type dyskerin.
Exposure to the precursors of 2,4-dichlorophenol and 2,5-dichlorophenol and to BPA, methyl paraben, and propyl paraben is widespread among Chinese adults > 40 years of age, with a smaller, but substantial and growing, proportion exposed to benzophenone-3, butyl paraben, and triclosan.
Based in Alaska since the late 1970s, Mr. Adams — not to be confused with John Coolidge Adams, the composer of "Nixon in China" — has made his reputation with a relatively small but substantial body of work.
The master bedroom has a smaller but still substantial terrace facing north.
