I bowled in a league in 1987-1988 when I was in my first post-college job. Here are my stats. I started off bowling a straight ball, then switched to a mild hook using a fingertip grip. That added consistency, but I also learned to use the marks for alignment. I don't bowl much anymore, but I still use the arrows to aim for my spares when I do go.

Game 1	Game 2	Game 3	Series	Average	3 wk avg
93	105	131	329	109.7
131	149	154	434	127.2
115	112	161	388	127.9	127.9
124	172	120	416	130.6	137.6
123	143	140	406	131.5	134.4
166	143	109	418	132.8	137.8
118	140	158	416	133.7	137.8
129	128	111	368	132.3	133.6
135	169	172	476	135.2	140.0
93	142	165	400	135.0	138.2
157	140	136	433	135.9	145.4
125	155	132	412	136.0	138.3
128	187	150	465	137.5	145.6
155	121	133	409	137.4	142.9
168	168	121	457	138.4	147.9
183	130	164	477	139.7	149.2
120	146	143	409	139.5	149.2
170	149	172	491	140.8	153.0
203	146	129	478	141.8	153.1
147	143	222	512	143.2	164.6
173	165	176	514	144.6	167.1
179	155	162	496	145.5	169.1
149	214	234	597	147.8	178.6
161	155	148	464	148.1	173.0
154	120	202	476	148.5	170.8
151	166	161	478	149.0	157.6
182	167	195	544	150.2	166.4