Dave,

You should be able to find examples in any of the more popular x/c
soaring books out there.

But I would suggest using a navigation system that assists you with
this calculation. You have a 302; add a PDA with GlideNav II or SeeYou
Mobile or WinPilot or XCSoar. These programs know the elevations of
your landing points, your glider's polar, and use current soaring
conditions (wind and MacCreedy) to figure out in real time what you
can get to, over your choice of safety altitude. Flying x/c becomes
much, much easier with a system like this, especially with higher
winds.

-ted/2NO