How to store Deja Dup full backup remotely

I'm keeping a copy of all my Deja Dup backup in my Dropbox. To conserve disk space, I'm wondering if I can delete the local copy of the duplicity-full.*.difftar, keeping only .sigtar to allow future incremental backup. I did try move away duplicity-full.*.difftar, Deja Dup end up prompting for back up password, so assuming it's going to do another full backup instead of incremental.