Solution with Modal_Forms Module

To add the required classes just do something similar to:

/**
 * Implements hook_preprocess_feedback_simple().
 */
function MYMODULEORTHEME_preprocess_feedback_simple(&$variables) {
  // Add modal_forms classes.
  $variables['class'][] = 'ctools-use-modal';
  // Uncomment either small, medium or large.
  $variables['class'][] = 'ctools-modal-modal-popup-small';
  // $variables['class'][] = 'ctools-modal-modal-popup-medium';
  // $variables['class'][] = 'ctools-modal-modal-popup-large';
}

If you write it in a custom module please contribute it back here.

A similar thread (for working with modal module) is: #1245908: how to use with automodal class?

It goes into a custom module...

Here I put it in a module for you... just download and unzip to your modules directory and enable.

I created a custom module using the module example code with admin settings and some extra features. What do you think about contributing back my custom module as a sandbox project for Feedback Simple Modal Forms?

Sounds good :)
I'm not opposed to including integration with these other modules (modal forms, automodal, etc) as submodules in this project!

do you have a project and git repository already created for this project? I can't find the project page

sorry rump, my bad, only noticed now that you're the maintainer and creator of feedback simple. Yeah creating submodules por feedback simple makes sense. I have a suggestion, add this modal forms integration as well choosing the path of the feedback simple button in the admin settings.

Can you verify the above module/code is still working properly? If so, I will commit it.

We already have another issue for admin settings.

Actually, now that I think about it.... All we need to do is add a classes field in the admin settings where people can type in ctools-use-modal.

I'll include this functionality in the other issue: #1407784: Add admin settings to change the image and destination URL

rump yes it is =) add a checkbox that adds that class automatically so people don't need to enter that specific class manually and add another field for custom classes. Add some php regex validation for security:)

Have been trying to get this to work with modal_forms V7.1 for the past couple of hours with no luck. Installed and enabled the patch in #3, enabled modal forms for contact page, and I'm still getting and HTTP Ajax error. How did you guys get it to work?

I'm also getting this error

There is a similar conversation about this error happening at http://drupal.org/node/1651226

The attached module in #3 used to work but is depreciated now.

Now that we had the admin settings with a class field, you can just input whichever classes are required for whichever modal module you're using.

For example:

ctools-use-modal

and one of:
ctools-modal-modal-popup-small (300x300)
ctools-modal-modal-popup-medium (550x450)
ctools-modal-modal-popup-large (80%x80%)

Also I think its probably important to acknowledge the Support Forums on the Automodal page:

Supported forms

Log in (modal_forms/nojs/login)
Request new password (modal_forms/nojs/password)
Create new account (modal_forms/nojs/register)
Contact (modal_forms/nojs/contact)

THE GIST:

The module in #3 is depreciated.
In Feedback Simple admin settings, try setting the class field to: feedback_simple ctools-use-modal ctools-modal-modal-popup-medium and the link field to modal_forms/nojs/contact