My best guess is the XTP data will give you a good starting point. OAL length is determined by the magazine and pistol. Dummy loads will help to figure what your OAL should be. I have read several people using 4.6 to 4.8 grains of W231 with 180 grain flat point Jacket bullets. This powder does burn a little dirty when you load to the low side of where it becomes accurate. Adding .1 grain of powder above the minimum accurate level often makes a cleaner burn and accuracy remains the same. If accuracy decreases, you probably already had the best load before adding that .1 grain of powder. Never exceed the max. listed levels. The max level normally is where a load starts to have spikes in the charge. You want to avoid that. Firing that first round you loaded is an experience you probably won't soon forget. It is more exciting than loading the round.
.40 is a high pressure round and not my first choice to start loading. Go slow and you probably will find a good load.