You made a really good job of that. I wondered how much it would cost to have someone make something similar for me over here in the UK as I have the mechanical aptitude of an ape...actually, that's an exaggeration, I suspect an ape has more mechanical aptitude. Having just had a quote for just over $1600 incl. tax I think I need a plan 'B'!
Did you consider just slicing the tank in two down near it's widest part and raising it by inserting, say, an inch or so of metal? I suspect that would be considerably cheaper for me to have done but I have no idea how much extra fuel that's likely to get me or if it's a practical idea.
To be honest I'm not after a lot. Solo I'm getting 220+ a little miles per tank. Two-up with luggage, which is how most of our biking is, I'm getting 180'ish. If I can increase the two-up range to the solo range without having to modify my riding that would be better.
Kevin