Just thought I'd point out - on the schematic L1 is labeled "1.0uF". I'm guessing this is supposed to be 1.0mH?
The thing I was blown away with after opening the plans is how simple (read: inexpensive) the crossover is! I've built 2-ways with twice as many components (not counting all the resistors in parallel).
Also, If I were to substitute a woofer with slightly less sensitivity (-2db), could I adjust the value of R5 and R2 to compensate? Or would this mess up the response? Normally I wouldn't mess with a good thing, but I've already got a great pair of McCauley 15's that would dig a bit deeper (in a larger box) than the 2226's.