Somewhere Ethan mentioned that you could chnge the number of rows that PlainText shows using CSS, but I looked at an example - http://thefarmschool.wagn.org/*css - and it looks like it's set in HTML? Saw this in angle brackets before the content of the card:
textarea rows="3" name="card[content]" id="card_content" cols="40" class="card-content"
what if you set the "height" in css?
yup, this worked:
.SELF-Xcss textarea {
height: 25em;
}