[Plugin: NextGEN Gallery] rebuild thumbnails while importing?

I am currently creating an import plugin that imports around 40,000 images, creates 14,000 galleries, and assigns them to post already published. Its all part of a much larger CMS conversion project for a client.

So far my plugin can create a NextGEN gallery, create a directory structure for the images, and import the images. However, I am having a hard time creating the thumbnails. I tried calling some of the classes in the plugin but that didn’t work. I also tried sending a POST command via cURL to the plugin to activate the “Scan Folder For Images” option, but the plugins use of nonce blocked that. Are there any tricks, plugins, or functions that I can utilize to build these thumbnails?

Thank you for the plugin and your time.

Thank you for your time.

https://www.ads-software.com/extend/plugins/nextgen-gallery/