Be very careful if you are talking about loading entire TrueCrypt files to SpiderOak or any other cloud services. Conduct extensive experiments to verify that SpiderOak will correctly identify which TrueCrypt file needs updating - it might or might not, depending on file size.
My own experiments indicated that once TrueCrypt files exceeded 4 or 5 GB in size, synchronization becomes very problematic. You can see a summary of these experiments at the blog: http://www.thriftslut.blogspot.com/2014/01/cloud-services-like-bittorrentsync-do.html
Basically, I found that several cloud services play nicely with many kinds of files except for TrueCrypt files.
These experiments suggest that the safest thing to do would be to mount the TrueCrypt file and then sync its contents to another folder which in turn would sync to SpiderOak. Unfortunately, this leaves you with a duplicate set of files that would be unencrypted on your computer. Or you might experiment with mounting the TrueCrypt volume and seeing if SpiderOak plays nicely with the files within the mounted volume and syncs them to the cloud. Either way, it's not a great solution to your problem and you, like me, might have to wait until cloud services develop a better one.
Hope this helps.