SOLVED. Children's book, girl with stump for arm called 'Thingy'. [s]

[bookel]

Possible ways to find it.
Search results.
Search results for 'ti:champions' > '1950..1984' > 'Book' > 'Fiction' > 'English' > 'Juvenile'

Champions
By Gloria Hope Hawley
https://openlibrary.org/works/OL53673...
unsure if that book is it.

[Lobstergirl, au gratin]

Christopher, are you still looking for this or did you find it?

[Lobstergirl, au gratin]

Did you rule out bookel's suggestion of Champions?

[bookel]

OK doing an actual Google Books Advanced Search (it's a specific search page for books, much more useful than Google at times).
Year range 1950-1989.
Books
Keywords: arm stump thingy.

First result
The Junior Bookshelf - Volume 44 - Page 137
1980 - ‎Snippet view -
This aspect of his writing is best illustrated in "Thingy" which involves a little girl born with a stump for an arm. His sound conception of the psychology of childhood, especially in relation to adults, makes each story stimulating if not challenging.

Look at snippet. Title and author visible.

POWLING, C. Daredevils or Scaredycats.
123 p. Abelard.
Collection of nine stories.

Copies and cover
https://www.abebooks.com/servlet/Sear...

Solved.

[Lobstergirl, au gratin]

Yay. Nice work bookel.