less bigger??

[Raymott]

Sally is a big girl. Jane is less big, but she's still too big to ride this bicycle.

[5jj]

On the note of less big however, I would recommend replacing 'less big' with smaller, as it does sound much more natural. .

'Smaller' is generally more appropriate, and is certainly far more common. However, in a couple of the COCA citation, 'smaller' not be more natural.

[Tdol]

There are 12 citations, so it's uncommon, but would you recommend that a poet, for instance, didn't use it? The odd and the unusual can sound great in the right hands. I would recommend smaller to most learners, but I wouldn't always do it.