[Replicant]

I'm still thinking the js method is the way to go. The form is submitted via ajax to the createcontent controller. If you can submit the form to your own controller function instead, forward the form data to the correct function for posting, catch the jsonResponse, and do your insert to your custom table at that point.

After looking at it a little closer, changing the data in the node table is going to cause issues with statistics, editing by post owner and also issues with attachments and images. There are more tables involved in the posts than just the node table that are attached to the userid. I would suggest staying away from changing the node table data and look at changing the output at template time.