There are a few shapes, depending on what you mean by 'optimal'. Most efficient looks like:
| Player 2 | 79 | ||
|---|---|---|---|
                    | |||
| Player 1 | 79 | ||
| Position ID: uO8PAAC47w8AAA Match ID: MAEFAAAAAAAA | |||
Optimal Racing looks like...:
| Player 2 | 79 | ||
|---|---|---|---|
 | |||
| Player 1 | 15 | ||
| Position ID: /38AAAC47w8AAA Match ID: MAEFAAAAAAAA | |||
Bear off efficient looks like:
| Player 2 | 79 | ||
|---|---|---|---|
   | |||
| Player 1 | 57 | ||
| Position ID: 2+4OAAC47w8AAA Match ID: MAEFAAAAAAAA | |||
Generally you look for triangle shapes though as relatively 'efficient'. So things like:
| Player 2 | 79 | ||
|---|---|---|---|
  | |||
| Player 1 | 62 | ||
| Position ID: bXcPAAC47w8AAA Match ID: MAEFAAAAAAAA | |||
Are also good - in general, depending on what you are trying to achieve, then aiming for smoother positions, or efficient positions are good - these should also act as guidelines for checker placement as you are bearing in.
I could be wrong (it happened once before), but these are what I use as target structures. Another good rule is if you have a choice, then getting a spare on the 4pt is most often quite good, and more efficient than a spare on the 5 or 3. You also are interested with bear off holes in making the hole less painful - so if you have a gap on the 2, then try and make sure that you can play a 2 more effectively (i.e. spare on 4pt). Same with the 3pt open, have a spare on the 6 so that you can slot the open point with the missing number. This does not apply to the ace point, unless you have several spares on the 2pt. Normally with aces you want to naturalize the back of a bear off structure - but thats entirely on a position by position basis, and it changes fluidly.
Look for the triangle. Consider that to be the type of shape to achieve both pre-bear off and during, and optimize as you go.
Keene