So you're still into the real nav thing don1reed ?
I havn't played SH3 for a while now. I wanted to try your suggestion, but the site stellarium.org doesn't work.
Another thing: what about the stock SH3 bug that the the ranges aren't displayed correctly on the navmap ? When you travel west, lets say to longitude of 50°W then this should be a shorter way if you are further north than (for example) directly at the equator.
Doesn't this bug disturb your calculations or do you just take them into account ?