Ngk Heat Range 7

I read on NICO to use #7 heat range if lightly modified.......and I also read that some have used #7's and ended up fouling out.  
My question is, how "lightly modified" do you have to be to use #7's without fouling??

Is #6 the normal heat range on the ca-det?
I do plan to use the NGK Iridium's since I don't wanna have to pull them every 4k miles to clean off like with coppers.

Should I just get #6's?

Ehhh, I just went ahead and ordered the 7's from sparkplugs.com  
If they foul atleast it's only 4 plugs now instead of 8  

Anywho, if anyone needs the part number for the Iridiums, it is
BCPR7EIX-11 or the stock number is 5691, which is also the same part # as the ca18et intake side, one heat range colder