There's too many posts to reasonably search.

The rules state that an LONEx can be upgraded to a DONEx.
I recall posts regarding changing a LONE3 to a LONE4 confirming that the prices used are the prices at the time of the ticketing/issue of the original ticket. Does this apply to the L --> D change as well? Is the answer different after the first flight is taken?

I'm reasonably certain that I want the RTW routing. The question is whether I can afford a (second) DONE rather than the LONE. Being able to purchase the latter now (locking in the price) would be an easier decision if the D price was also locked in...

And of course this is made more interesting by the ability to issue the RTW on the basis of the original starting point from any country and current currency changes.

Happy wandering

Fred