Its not necessary to double strip to put up a more challenging shot than the THS.  Also, something nobody mentions is that bowling in a sport league isn't going to do you much good unless you have the opportunity and commitment to practice on the tougher patterns.  Most bowlers who don't have experience on flatter patterns are going to have to make changes to their game if they want to significantly improve.  Single biggest thing that would help most bowlers is learning to go straighter.  It doesn't mean throw less ball, just lowering the axis rotation, and getting comfortable more squared up. 

The biggest thing about tournament patterns is the distance which can be much longer or much shorter than a house shot.  Bowling on tournament patterns is more about becoming versatile than it is about making better shots.  Versatility is the hardest thing to develop on a 40 foot house shot.