For the past few seasons, I have been throwing end over end straight shots at spares.  Have been converting reasonably well, but have noticed a few times a small amount of side rotation has caused some inaccuracies.

I did this because I was having fit issues with spare ball over the course of several games, resulting in sticking/dropping my plastic ball.  Also, It was adding another ball to my bag / the ball return.

Now I've made a few grip changes that has reduced swell/change in thumb size over the course of several games, so I think that should be solved.  Hoping this change will convert 1 additional spare per set...which over the course of a season makes a big difference in average.

Ordered a Polar Ice today. :-)

I'm a fan of plastic. I just bought a new Bam and its lovely.

I am a big believer in spare balls, although I prefer urethane to plastic.  If nothing else it extends the life of your strike ball.  Also, on fresh tournament patterns the spare ball really makes a difference, as much on left side spares as 10 pins. 

I was an extremely accurate spare shooter, but I never, ever used a so-called spare ball. Early on, I found out that when I used my regular delivery while inserting my ring finger and my little finger into the holes, the ball would go virtually straight on any type of lane conditions.

Such a "wrong-finger" delivery proved especially valuable while attempting to convert 10-pins, 3-10 baby splits, 6-10s and 3-6-10s. I'm sure that there must be others who use that technique, but the use of "spare balls" is obviously more conventional.

Mighty fish, I have bowled league nights like that when I have hurt my middle finger at work before. It takes a few revs off, but the ball still hooks for me

Dear lilpossum1:

Whereas I was deadly accurate, I never rolled anywhere near a powerful first ball, so I have no doubt that your delivery would result in a stronger (and bigger) hook than mine.