Kahler, did you get around to brewing your recipe? I'll be interested to see how you like it.
I've been doing some homework on this clone recipe and I came across the Basic Brewing Radio podcast from October 23, 2008 where they interview the head brewer at Odell Brewing Company:
http://www.basicbrewing.com/index.php?page=basic-brewing-radio-2008
Scroll down to find the Oct 23 episode. In the middle of their conversation with Odell's brewer they bring up the IPA. The brewer implies they use just perle and chinook in the boil. The flavor and aroma additions must be in the whirlpool and the hop back. Also, next time I brew I'll move the amarillo to later in the boil...like maybe 5 min. And I'll use some ESB malt in the grist. Odell mentioned that they boil for 90 minutes. Depending on how much LP is left in your tank, that may be worth trying too.
Happy brewing!