The phrase "ample allowance" is correct and usable in written English.
It can be used to refer to a generous or sufficient amount of something, often in the context of time, resources, or permissions.
Example: "The project was given an ample allowance of time to ensure that all aspects were thoroughly addressed."
Alternatives: "generous provision" or "sufficient margin".
When land is well prepared, half a bushel of seed is an ample allowance for an acre; the rows being at nine inches from each other, and the dibble holes at the same distance in the rows.
This "architecture of pain," as psychoanalyst Jacques Lacan says in another context altogether, was my model for a long while, a model that I am trying to reconstruct today, with ample allowance for punctuated lacerations and weak points meant to bolster part of my psychic suppleness.
The Mediterranean diet exalts olive oil, recommends restraint around red meat and makes ample allowance for pasta, which Michael Romano, the executive chef at the Union Square Cafe in Manhattan, described as a safe harbor in a confused culinary universe with "layers of mad cow disease and crazy chicken disease".
If you were to draw a line attempting to demarcate the territory thickest with Yankee sympathizers from that thickest with Red Sox fans, making ample allowances for infiltration, you would start a little east of New Haven (a Yankees town) and kind of slant north and east toward the Connecticut River.
There is ample sentencing allowance in all of the guidelines for the most serious case.
But the ample housing allowance enables them to live in one of Westchester County's finest school districts, and, of course, there is no language barrier.
I would like to say that my divorce provided for a comfortable life style, with an ample living allowance for me and our daughters.
Minnesota, by contrast, has offered ample assistance -- cash allowances to supplement income, job training, more opportunities for health and child care -- in addition to requiring that welfare recipients work.
Although long-held income guarantees for all laid-off union members are largely gone, the most veteran senior U.A.W. workers still have healthy wages and pensions, generous health care benefits (although not the fully paid premiums the union once enjoyed), ample vacation time, and cost-of-living allowances on top of hourly wages, a benefit given up at Ford.
