Burning HD 1080i projects to standard DVD

[AndyMac]

Hi there,
I've made a small 2 minute trailer in HD in VS11+. I want to burn it to DVD, but retain its HD quality. I can create an HD file, and even burn the project to DVD, but in the latter its quality is downgraded to SD because of the bitrates etc for burning to that medium. The spec sheet for VS11+ says HD projects can be burned successfully to standard DVD and retain their HD quality, but I'm not sure how to do this? I do not have an HD disc burner. I notice, however, that if you change the settings cog at the bottom of the VS11+ share page to an HD DVD, it offers better bitrates etc than for the standard DVD. But altering these settings and trying to burn to standard DVD has thusfar proved unsuccessful.
Any advice is welcome. If this subject has already been broached, please feel free to suggest the thread location.
Regards
Andy M