I have a little problem with your plugin. I need to output your form in fancybox2 window. Fancybox2 requred the id for getting content. But you get form id from id post and some one else(I dont know).
I solved this problem by replase string
$form = '<div class="wpcf7" id="' . $this->unit_tag . '">';
on
$form = '<div class="wpcf7" id="' . $this->title . '">';
And now I can give stable id for form.
Maybe some one have another way?