Hi Mark,
According to his article, and if you're using the first box suggested then the notch requirements are:
L1 - 0.7mH, 19 ga air core (.41 dcr)
R1 - 6.8 ohm, 10 watt non-inducitive
C1 - 8.2 mfd poly
The second/third boxes use C1 - 3.3 mfd poly
If you haven't got the article then email Zaph, I'm sure he'll email it to you, or I can email it you for that matter if Zaph has no objections.