I wanted to make the twitter feed area larger than the small size the Itasca template gave me. Using the "inspect" function in Google Chrome, I was able to come up with the following code that lengthened the ".tweet-container" element 'block-size' dimension (the size of the total twitter feed area, and the accompanying ".tweets" container area, the 'max-height' value, the area that actually displays the content of the tweets. I found you have to change both the .tweet-container block-size and the .Tweets max-height value, keeping the .tweet-container block-size 150px larger than the .tweets max-height value in order for it to display properly.
I haven't tried it with any other template but it works well with the Itasca template.
border-top: 1px solid #eaeaea;
border-top-color: rgb(234, 234, 234);
border-bottom: 1px solid #eaeaea;
border-bottom-color: rgb(234, 234, 234);