Here's the shaft flex you should play based on your swing speed
Stiff vs. Regular Flex: Which Golf Shaft is Right for You?
Amazon.com : Mens Complete Golf Club Set Stiff Flex - Ti Forged Driver, Fairway Wood, 3,4,5 Hybrids Irons, Sand Wedge, Putter & Stand Bag Right Handed : Sports & Outdoors
Here's the shaft flex you should play based on your swing speed
Which Shaft Flex Should YOU Use?... Don't Go Wrong! - YouTube
Golf Shaft Flex: Stiff vs. Regular and How It Affects Your Swing Speed | Curated.com
Your Golf Club Shaft is Too Stiff
What Happens If Your Driver Shaft Is Too Stiff? - The Expert Golf Website