I came across Stan's sale page. Some good stuff on there including castor correction plates. Here's a link to 80 manual drop boxes. Cranked arms are I guess technically THE best solution, but these solved all of my issues.
https://the-overlander.myshopify.com/collections/sale/products/boss-dropbox-set
https://the-overlander.myshopify.com/collections/sale/products/boss-dropbox-set