I've got a stack of wood that I don't think we will ever burn. I might try this this spring. I don't think I'll go for 7' tall though.
...try it. Write back. Lemme know how it goes.
Something to keep in mind about Hugelkultur is it's championed by Sepp Holzer, who is not a member of the science-based community. His largest claim to fame is turning a 100-acre conventional farm into a 100-acre permaculture farm, thereby slashing its yields by about 80%. Something else to keep in mind is that Paul Wheaton is... a flake. He has a youtube video in which he threshes grain in a Home Depot bucket with a cordless drill and some zinc-plated Chinese Home Depot chain... and a podcast in which he castigates some poor cottage-industry canning company husband-and-wife team because the plastic lids of their jars might (might) contain "chemicals" since they're only "food grade" and the couple didn't investigate further than that. He also champions rocket-mass heaters as the way to provide cheap warmth but when he needed to heat his apartment he set a 100W bulb over his head and bought a heated mousepad.
I'd say do one raised bed, then do another raised bed with a log under it and lemme know how it works. This stuff is dear to my heart and quite important but there's an awful lot of woo and not a lot of science to some of it.