So I enabled by 250Gb USB drive connected to my 865L and set up a user account for my self and gave ROOT access, saved settings and rebooted the router. I put some files on the drive, text, video, photos, music and such on the drive. After the reboot. I opened SP mobile on my iPhone 4S and all the files were seen and usable. I think I need to find other video files that are smaller, would play the MKV files. Did play the music ones and test and pdf files displayed. I'm not using any reserved IP addresses. Most of the settings are default right now as I haven't changed any thing as I want to see how this thing run out of the box. I presume using the same process on the 826 should work.
Keep us posted.