i dont think an unparsed iso file in dom0 is that dangerous, esp if you trust it enough to make a template vm, but i think the less we do in dom0, the better.
as an alternate, may a special vm just for making the hvm? could be good for trying an os when you dont even trust the iso it came from.
If the iso resides in a vm all You need to do is do it like this (assuming the VM which holds the iso is named test and the hvm is named test2)
qvm start test2 --drive=:test\path\to\.iso
Remember to put \ character if You have spaces in the directory path or rename the files\catalogues so the names don't have spaces.
thanks! i didnt scroll down far enough on that page :)