You can always check your distance measurements, but if they are close, then you should be good. If you have a ford with easy entry/exit (where your seat moves backwards when key is removed and forwards when it is placed in the ignition) make sure your keys are in the ignition prior to measuring. I messed that up a couple times and had bad measurements.
If the distance measurements are good, get a 9v battery (or any battery but 9v makes it easy to see) and test the speakers for polarity. Hook the positive side that goes to the speaker to positive on battery, and negative to negative. This should make the speaker move out (reverse the connection and it moves in), all speakers should either move out, or all should move in (doesn't matter as long as they all move the same way). If a set moves opposite, you have them wired wrong.
If you can't do this, there are some apps for polarity testers, but they aren't quite as good, but work for speakers you can't see easily. I still prefer doing the 9v and using a flashlight to look through the grills to make sure, but that does require a second set of hands to connect the battery for most people.
Not that any of this really matters if you do have them summing correctly.