It takes time and patience to grow a Sport League, Ours is up to 28 after 5 seasons. Peers have to talk about it then people start to come and see what it is about.

I've bowled in a summer sport shot league for about 6 or 7 years.  We started with about 10-12 Three person teams.  This year we have 4.  Most people who left are frustrated or clueless. 

There is also a PBA shot summer league.  This is the second year.  We had 12 two-man teams the first year.  We have 9 this year.

I think the best thing to do on house patterns to hone your game for sport patterns is to work on a more direct game with less axis rotation ( not lower revs ).  I learned even as a kid that swing area is addictive.  Learning a release that you can keep in front of you ( the new buzz phrase ) and still maintain a free approach and arm swing is important.   

You cant over power flat patterns, or find a magic line or magic ball.  That doesn't mean you cant have a roll that can give you some margin of error or give you some carry.  There is more than one way to handle flat patterns.  The biggest problem is that the more you want to hook the ball, the more one dimensional you become when they start varying the length of the patterns.     

I started a USBC sanctioned scratch/sport league this year.  We have 21 bowlers (seven 3 man teams) and no prize fund.  The lack of a prize fund is what makes things better imo.  No one cares about "winning" the league and since people don't care about winning the league, you can bowl with whoever you want and have some fun.  No worrying about a draft, average cap or anything other than just bowling with friends. 

People of all averages do want a challenge, but the lower average bowler views scratch leagues and even more so, sport leagues, as a way for good bowlers to kick their ass and take their money.  Removing that "you suck so you lose" factor seems to be attracting bowlers of all averages.  The lowest average bowler we have is a 196 THS average...he's at 140 in the scratch/sport league and he's having a great time.

We do run pot games and brackets for those who want to mix things up a bit, but no one is forced or guilted into entering those. 

Something else that helped bring people in was the fact that the USBC removed the extra $15 sport sanction this year.

We'll see how things go as the year progresses.

Frustration is the main reason bowlers quit competing on sport shots.  I feel education is the reason for the frustration.  Your average sport shot bowler knows the shot is more difficult.  They may know the general layout of the pattern.  But they have zero idea how to attack the pattern to optimize their success.

I used to host a sport shot tournament once a month.  I would post on Facebook the pattern along with links to YouTube videos so bowlers would get an idea on how to attack the pattern.  Some would come to the tournament and start off based on what they may have seen online.  These bowlers would do well.  Some would start with their league equipment and stand where they always stand during league and bowl just like it was league.  These bowlers rarely cashed.

After everything was done, they just couldn't realize why they couldn't score.  The fact they may have to throw a different ball or throw the ball on a different part of the lane or, heaven forbid, throw the ball with a different release doesn't occur to them.

If sport shot leagues are to be successful, there has to be some education for the bowlers.  Visually seeing or listening to those who are successful on the conditions will hopefully give them a better understanding of what it takes to be successful, and in return have more fun.  Having more fun will increase participation.

A small house about 40 minutes from me puts out a sport shot no tap tournament a couple times a month. Great way to work on your game for cheap.