i intend to eventually do what you are currently doing, split the downloads and the forum on 2 different hosts. I dont know if there is a mod or an article that helps to do this, but if there wasn't i was hoping to try use a combination of .htaccess redirects and dns settings.....have no idea how though, just figured that i'll cross that bridge when i come to it
EDIT: bookmarked....want to know if someone can help you
EDIT2: found this thread with the search function.....its a pretty useful thread, read through it all, but the most important post is #17.
https://vborg.vbsupport.ru/showthread.php?t=110291