I've been using Northern Brewer kits for most of my batches so far, and I've been doing full boils on their kits that have instructions for partial boil.
I contacted NB and they said it's fairly easy to do a full boil on these kits:
1) If there are any late extract additions, ignore them and add all of the extract at the start.
2) Follow the hop schedule on the All-Grain version of the kit.
part 1, easy. part 2, also easy since their all-grain kits typically have the same hop schedules.
My question here is if this the correct way to convert. So far the recipes have turned out anywhere from "OK" to "great" doing it this way (starting with 6 gallons, eventually boiling down to just over 5 gallons when finished). Let me know your thoughts on this, I'm planning on experimenting with my own recipes soon. I'll probably start by modifying a known recipe and see where it takes me.