Since I have yet to ride this year   I am signing up for the 40 miler.  Would enjoy some company.  I don't remember the 20 having any intimidating hills, but the 40 and 60 will definitely test all of your gears.
 
http://www.tourdenorway.com
 
The fourth Bosque Tour de Norway will be held on May 16, 2015. The start/finish line will be at Clifton High School. We will have 4 routes to choose from 20, 40, 60 and 80 miles. Each will allow you to enjoy the beauty of the top of Texas hill country and be riding through the historical Norse community.
 
$25
 
WHAT TO EXPECT:
You will be riding on a combination of state highways and county roads. All are paved but there are some rough areas on the county roads due to chip seal pavement and some potholes. Most roads are comfortable to ride on. Since this is the top of the hill country there are rolling hills with a few good leg burner climbs, followed by fast descents.

Quote from FlyingLaZBoy on May 4^th, 2015, 9:02am:

 
Define serious, please.