Low top weight balls tend to roll slightly earlier than higher top weight ones (like short pins do so more than longer pins).  What kind of equipment you'd need to measure that is a different story.

If you're worried about how your statics will end up (like too much bottom weight in the drilled ball), you could try drilling your fingers as shallow as possible.  For a fingertip drill, you really only need a little more than an inch, if that much, especially if you don't use grips (can't remember if you do or not).  Same for the thumb.  There's probably a "standard" depth for those holes to accomodate grips or thumb sleeves, but with a little zeal, you could drill them shallower and trim the inserts.

SH

Ramtart,

  In todays modern equipment, topweight actually is a minor factor in deciding ball reaction. ( Unless you have some exotic drill with the topweight shifted so far it becomes sideweight, then you have to be careful)

  I've been told that if you play a drier house you need more topweight to help the ball get through the heads better with a slightly sharper backend, and if you play an oily house, lower topweight will help the ball get into a roll sooner.
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"The difference between stupidity and genius is that genius has its limits."
Albert Einstein

I think I'll just go out and buy a new target zone with 1.5 ounces of topweight then and use it for oil.

The level of backwards thinking in modern bowling ball drilling astounds me.
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stanski

Ramtart I don't feel you should worry about the ball having low top weight.  I used to think that the top weight made a big difference.  I don't feel that way anymore.  I have had some low top weight balls hit very hard and carry great.

I feel we as bowlers should really pay more attention to the surface of the ball.  That's why I feel 1 layout in an arsenal can do the job for the most part.  Just let the cover and cores seperate the reactions.

I personally use 2 different layouts in my arsenal.  Just match the surface up to the condition and be good to go.