Canuck's your man... for my SP01 Shadow, I use 1.15 for the flattened-nose, and 1.125 for the round. It's all about where the shoulders of the bullets hit the rifling. Too long and it may not lock-up properly, or the bullet may get squished into the case, or it may not clear the mags, etc, properly. Too short, and you get dangerous case pressures.
I actually took a Dremel tool, and cut a two gashes in a sized brass. I lightly hand placed a bullet into the case neck, and the bullet went in loosely. I chambered it, ejected it, and measured the max OAL to the lands (I don't remember the measurement, which tells you that was a bit of a waste of time

)
If in doubt, load 50 in 1.125" (that's probably the longest you'll see in the recipes). Shoot them off, and see if you have any feed problems (stick a chrony in front and measure the speeds). Shorten as needed, but adjust the powder if necessary.
It's easier, I think, for sports like IPSC, where we tend to load on the light side (just above power factor). If you were playing with Max loads (+P), you'd have less wiggle room...