A: I like having a MINI Cooper. I sort of identify with it. You know? It’s pretty little. I feel as if it’s proportion… that we are in proportion, you know? Me and my car, we are sort of… together, facing the rest of the world. (So you understand, the speaker is little and short.)
So you understand, the speaker is little and short. What does it mean “in proportion”? Just literally, the speaker is little and the mini cooper is little and the car is the right one for the speaker?
The Cambridge Dictionary defines proportion as,
the correct or most attractive relationship between the size of
different parts of the same thing or between one thing and another:
His feet seem very small in proportion to his body.
My head was much nearer the camera than the rest of me so I’m all out
So yes, you can say, ‘We are in proportion.’
‘I feel as if it’s proportion… ‘ is less idiomatic but perfectly acceptable if the speaker is groping for the right expression.