Need help modding Impex

[mgaretz]

We are migrating from WowBB and for the most part Impex is working fine.

I added the mod to vBulletin for thread descriptions (because Wowbb has them and we don't want to lose them). The mod is working fine for new posts. The mods a coulmn to the threads table called threaddesc. I have modded the 006.php impex file to add:

$try->set_value('nonmandatory', 'threaddesc',  $thread_details['topic_description']);

And I've added this line to the vbfields.php file:

$queries[] = "INSERT INTO {$tableprefix}vbfields VALUES ('title', 'thread', 'Y', 'threaddesc', 'return true;', 'vbulletin')";

But the topic descriptions won't import. What am I missing?