The phrase "ample if not" is correct and usable in written English.
It can be used to suggest that something is sufficient or more than sufficient, often followed by a comparison or an alternative.
Example: "The resources provided for the project are ample if not excessive, ensuring we can meet our goals comfortably."
Alternatives: "sufficient if not abundant" or "adequate if not plentiful".
Medieval exegetes provided ample (if not always persuasive) justification for the Bible's choice of these particular branches and fruit as symbols of rejoicing.
The brakes have ample, if not impressive, stopping power, and the antilock system worked well enough to save me from some scrapes when stopping short in the rain.
We took an afternoon excursion to Cayo Santiago, a half-hour motorboat ride, where the surrounding coral reef provides an ample, if not abundant, variety of fish.
Even though their style may be very different from Annie Landau's or Brooke Astor's, New York women of a certain age who possess ample, if not necessarily unlimited, means continue to appreciate the importance of looking their best.
Caterpillar then funneled $1.3 billion into it, charging workers fees that were quite ample, if not out of line with averages in the mutual fund industry: 1.12% annually for a value fund, 1.54% for an international growth fund and so on.
Breakfasts at both Samaya hotels are ample if not world class.
Michael Corvino endowed his portrayal of Iago with ample vocal color if not much dramatic savvy beyond a few elementary "I am the villain" gestures.
"The vote count was useful to show that all points had an ample consensus, even if not two-thirds," he said.
In this hospitable setting, works by 80 of the arts council's members have adequate, if not ample, space.
Each floor has 17 individually designed rooms with ample space and tasteful (if not high-design) minimalist furniture.
He has a four-bedroom house with a kitchen and living room, which would be ample if there weren't 12 people under his roof.
