I still use adbfire
https://www.androidfilehost.com/?fid=24566466246344871 to load Kodi
I am putting custom hevc x265 4k rips on the box now bud. Danamy has confirmed working fine over firestick. I will load the lot of them on in 2 weeks as we move to a 30TB server. x265 is advancing fast the only reason you do not see loads of rips is because of compatability with devices, the scene will not have a dedicated x265 section for about 3 years. The scene council is notoriously resisitant to change but some of us do put out 4k rips, group -DAA for example are very progressive in this arena and push the standard hard.
For now though you will have to live with me doing them for you...which ironically will end up being close to the spec scene deems viable.
Test this... NEW MOVIES\Deadpool.2015.1080p.BluRay.x265.INTERNAL-FLAME