Sounds nice. Haven't tasted any beers with Riwaka yet, but it sure sounds very interesting. Thinking about making an APA with Riwaka and Amarillo to get a real passionfruit punch... Dunno about the chocolate malt, though. I'm really not a big fan of too much roasted flavors in IPA's, but if that's your thing, go for it. I feel that it often blurrs the hop flavors and aromas, though.
Keep us posted, then. If it turns out well, maybe I'll order some Riwaka soon... =)
Primary: Ordinary Bitter
Secondary: Centennial IPA
Coming up: Beamish style Dry stout, Hefeweizen, Dark Mild