full 1080p 3D on YouTube

I use wmv in SBS half and set the resolution to 1080 x 1920. In YT you set the 3D to "already is 3D"

After YT processes your upload it will show up with a list of resolutions maximum OS 1080p.

You could also use mp4 but the file size on upload is a bit bigger.

David-
What you propose is extremely unconventional formatting for several reasons. Not saying it can't be done but to do that might need some form of hack to YT rules to upload. They require SBS half for pre formatted 3D. This is a full frame 1080 x 1920 divided into two squeezed images 1080x960 side by side. If you mess with that rule for YT then it's software wont know what to do with the file. Weird things may happen.

You may wish to experiment with other compression formats to improve quality over what I suggested. Start with h.264 or mp4. I have used these too but they give barely noticeable improvement in image quality and suffer upload time as the files are considerably larger.

Another thing I have done in the past is create a full resolution 3D blu ray ISO file in Vegas Pro and upload that to my own server. this, I guarantee will get you the maximum quality your production equipment will do but this costs in both time and money. I have my productions, Valley of Fire, and Bryce Canyon on my server in full 3D blu ray ISO files. The recipient has to download a multi gigabyte file and then burn it to a blu ray 25 gb BD-R to play. I think only about 30 people have downloaded these files. For the rest "normal" people, YT is good enough for them.

If they were uploaded that way (and most of them are), then yes. I have seen a handful that are encoded over-under, with each eye at 1920x540, but I've found the result is a very soft picture. I prefer HSBS myself.