Start with just bumping it 1 notch and if you're still frustrated with too many lazy flys than go 2. I found 1 to be the sweet spot for the most part, but sometimes I'll bump it to 2 if I'm scuffling. Trust me though, it makes a HUGE difference and is the best slider to bump if you're struggling with too much weak contact. The actual Contact slider isn't what you want to mess with since that will only make it easier to get the bat on the ball, and may actually increase lazy flys since you're putting more balls into play that otherwise would've been a swing and miss or a foul. The Solid Hits slider on the other hand will increase the quality of your hits and help you to drive the ball more consistently, which will also lead to more HR (which is why you don't really need to increase the Power slider either).
The bottom line is this one tweak alone made the game feel right again after the patches for me.
Hope this helps others as well.