Increase Length of Captcha Description Field to 256

Thanks for the great module. Would it be possible to increase the #maxlength property of the captcha_description field to allow for more than the default 128 characters. I find I need more space on the form to explain to my users what this is all about. Perhaps other people would like this and it's not going to present any significant downsides. Can I suggest that it's increased to at least 300 chars?

Thanks in advance.