I was (a) measly five

[Mnemon]

a. He was about seven feet tall while I was a measly five.
b. He was about seven feet tall while I was measly five.
c. He was about seven feet tall while I was just measly five.

Hi.
Are they all correct and idiomatic to you?

 

[Skrej]

Only the first one works for me.

 

[Rover_KE]

Yes. - the others are incorrect.

 

[Tdol]

You need the indefinite article in all, after just in the last.