To get 6 districts' worth of D+7 territory, you'll need to find a way to create 2 GOP sinks that are at least R+20. That's not something you can do in DRA alone.
I've always said that WI is one of the most ruthless gerrymanders in the country - and one of the hardest to break (outside of a true wave or massive Midwest resurgence) - but the state's population distribution definitely plays a huge role in why it's so easy to gerrymander.
A "fair" Wisconsn that I drew
here is 2 Safe Dem - 2 Toss Up - 2 Likley R - 2 Safe R.
People don't realize how gerrymandered Ryan's district is. He probably loses multiple times since 2002 if his district looked more like it did before. Adding the rest of Rock County and taking out most of Waukesha County makes this a pure toss up seat.
If the North is 100% gone to the Democrats (which I don't think is necessairly the case) and if the West is going that way (definitly don't think that's the case), then the only way to get close to a split 4-4 map is to split Milwauke County and Dane County.
