Possible to import non-Activity Fit files?

I recently switched from Fitbit to Garmin.  I've been fooling around trying to generate some Fit files from my Fitbit data using the Java SDK.  Initially, I was focused on sleep and "monitoring" data, rather than activities.  Are there any tools to validate non-Activity Fit files?  When I try to import a generated file, I get an error.  However, the Fit To CSV tool validation is focused on Activity files and does not even correctly validate Fit files exported from my Garmin account.  Any direction would be most appreciated.

Thanks,
Craig