For a chart we put together on SPL vs. height for typical pool length distances, download this: http://www.totalimmersion.net/store/...l#.VzM7q2YuogU
We don't use SWOLF much. it mashes two metrics together which hinders your ability to really figure out what is wrong with your technique.
There are 4 metrics that are measurable and important: distance you swam, time to swim that distance, stroke rate/tempo during that distance, number of strokes you took. holding the distance constant is very easy if you're in a pool, so you're then left with 3 that you can manipulate. the hardest was tempo - without a tempo trainer (TT), it's pretty much impossible that you can maintain a certain tempo consistently. but we love the TT because now we can make that variable constant. once we can do that, we have a lot of accurate means to really dive into what are the problems in your stroke and where it breaks down.
here's a free TT guide: http://www.totalimmersion.net/store/...l#.VzM9E2YuogU