Hey Talismansa,
i got it to output it via adobe premiere. Here you can go for 4k resolution. Just resize the left and right images by 50% in height and line them up so that they both giving 100 % of the 4K Top/Bottom picture. In the newest version you can write metadata for vr files needing for youtube. so all is perfekt for uploading it there.
there is a 7 days trail version of the premiere CC.