Set line limit in textarea tag?

I have a textarea field which by default gives me 10 blank lines of text and I would like to make the field shorter, ie limit it to 6 blank lines. If I understand the (size)/(maxlength) tag option, the example given (40/100) relates to character count and not to line count – but this is an address field where users will enter different line lengths broken up by carriage returns, so a character limit doesn’t work (anyway, the width of the input area is plenty long enough for the longest place or street names).

If I can’t set a 6-line limit in the tag, should I simply target the visible height of the input area with CSS so that the window is only 6 lines high?

Thanks for any help.

https://wordpress.org/plugins/contact-form-7/