if your base is 6mg nic and you are trying to mix 6mg nic, you are SOL - if you add flavor, nic level is going to go down - in general, you are looking at 10-20% flavoring with Capella (genrally 15% or up)
is cloud 9 a flavor company? not familiar with 'em
also, keep in mind, most flavors are PG based - so, adding flavor to that base will also raise your PG level
best suggestion is get a recipe for a juice you have tried and like - then plug some numbers into a recipe calculator (ejuicemeup is what i use) to find out, based on flavor percentages, desired nic level, PG/ VG levels what components to add in
with a bottle of 6mg nic base at 70/30 vg/pg level, you are going to have some challenges - especially with no recipe - for example, if you add 20% flavoring to that base, you will end up with a 4.8mg nic level (roughly) and about a 56/44 vg/ pg level (may be off a little - just running numbers in my head)