steveb077,
virtual high-5! i installed the EXACT same pair of Hellas over the weekend. Plus I changed the stock wiring to thicker custom ones, and added in a extra relay that draws juice straight from the 12V battery.
Man, i LOVE these new Hellas. They sound so sharp and loud v.s. the pissy OEM ones we have (which are crap. i guess the Japanese are way too courteous to use their horns?

)
Like your custom install job, but I decided to space mine out and install 'em on a custom mounting bracket...
before i went w/the custom-iron-rod approach, i mounted the horns side by side, using the existing OEM horn mount point, just like you...
then i realized if you space them out a little, the sound is a little clearer. a little sharper. and a little louder (which to me, makes a big deal! since i want volume over quality)....
if you want to improve over your v1.0 job, try reinstalling & spacing them out a little... you'll notice a slight - but immediately welcomed - change in sound volume