Not very scientific, but that's the general idea.
More precisely, you can figure out shift points using a dyno sheet. Take a dyno sheet and plot the speed vs rear wheel torque for every gear (I use excel). Where the torque lines cross are ideal shift points.
I've done this using a dyno sheet from a stock NPI engine. The theoretical shift points are: 1-2 at 5600, 2-3 at 5400, 3-4 at 5000 and 4-5 at 5400. Notice the greater the change in gearing, the higher the ideal shift point. For example, the 1-2 is pretty steep, from a 3.37 in 1st to a 1.99 in 2nd. Same for the 4-5 shift, it is a bit steep, so it pays off to rev a bit higher before shifting.
My syncros have 145k miles on them, and don't like shifting that high, so I was shifting a bit sooner. I'd expect a PI engine to like even higher shift points than what's listed here, but the pattern will be the same: Run out 1st far as you can, it has a huge gearing advantage, run out 2nd nicely but not too far, short shift 3rd. Then, if you haven't won by the end of 4th, you probably not going to...