Ok, because of the fundamental differences between GET and POST, even using ad_return_url isn't going to fix the redirect issue in every case. For instance, if the form has a file upload widget, or you reach the length limit of a URL (around 2000 chars in IE
https://stackoverflow.com/questions/417142/what-is-the-maximum-length-of-a-url-in-different-browsers ), it will break.
Having said that, it is an improvement on what is currently there. So, if you are confident that you don't have file uploads or lots of large fields that would put your over the URL length limits, you could try it, as a short term measure.
A more complete solution to the problem would be to implement some way to store the form data in Naviserver, and after the login redirect, recover the data. I'm not quite sure what the best approach to this would be. Would be good to get opinions from others here.
Brian