You are correct on 1 point.  USBC allows you to have 3 ounces TOTAL between top and bottom weight only.  So if you have 2 ounces of top weight, you can only have at most 1 ounce of bottom weight to make the ball legal.  Usually you don't end up worrying about this when you drill because your fingers and thumb will usually take around 3 ounces out, that is why the manufacturers and top weight to the ball before you drill.

Hope that clears it up for you.

Also, the Jayhawk website has a section on how to weigh a ball using a Kaufman scale and in their it describes the legal limits as well.

Roto4ever

Roto4ever is a little mixed up.  A bowling ball has either top weight or bottom weight, not both.  And the amount of allowed imbalance varies by the total weight of the ball.  The specifications, copied from bowl.com, follow.  --  JohnP


Balance:
The following tolerances shall be permissible in the balance
of a bowling ball used in certified competition:
1. 10.01 pounds or more:
a. Not more than 3 ounces difference between top
half of the ball (finger hole side) and the bottom
half (side opposite the finger holes).
b. Not more than 1 ounce difference between the
sides to the right and left of the finger holes or
between the sides in front and back of the finger
holes.
c. Aball drilled without a thumb hole may not have
more than 1 ounce difference between any two
halves of the ball.
d. A ball drilled without any finger holes or indentations,
may not have more than 1 ounce difference
between any two halves of the ball.
e. A ball used without any hole or indentations
may not have more than 1 ounce difference between
any two halves of the ball.
f. Any ball used with a two-handed delivery
without holes or indentations may not have more
than 1 ounce difference between any two halves
of the ball.
2. For a ball weighing 10.0 pounds to 8.0 pounds:
a. Not more than 2 ounces difference between top
half of the ball (finger hole side) and the bottom
half (side opposite the finger holes).
b. Not more than 3/4 ounce difference between the
sides to the right and left of the finger holes or
between the sides in front and back of the finger
holes.
c. A ball drilled without a thumb hole may not
have more than 3/4 ounce difference between
any two halves of the ball.
d. A ball drilled without any finger holes or indentations,
may not have more than 3/4 ounce difference
between any two halves of the ball.
e. A ball used without any hole or indentations
may not have more than 3/4 ounce difference
between any two halves of the ball.
f. Any ball used with a two-handed delivery with
or without holes or indentations may not have
more than 3/4 ounce difference between any
two halves of the ball.
3. Less than 8.0 pounds:
a. Not more than 3/4 ounce difference between the
top half of the ball (finger hole side) and the bottom
half (side opposite the finger holes).
b. Not more than 3/4 ounce difference between the
sides to the right and left of the finger holes or
between the sides in front and back of the finger
holes.
c. A ball drilled without a thumb hole may not
have more than 3/4 ounce difference between
any two halves of the ball.
d. A ball drilled without any finger holes or indentations,
may not have more than 3/4 ounce difference
between any two halves of the ball.
e. A ball used without any hole or indentations
may not have more than 3/4 ounce difference
between any two halves of the ball.
f. Any ball used with a two-handed delivery with
or without holes or indentations may not have
more than 3/4 ounce difference between any
two halves of the ball.
DRILLING SPECIFICATIONS
PAGE I-3 (Oct. 08)
LS RS
THUMB HOLE
(BACK

Just to answer the question. YES if the ball weighs over 10.01 AFTER DRILL you can have up to 3.00000000 oz top or bottom, NO MORE!!!!

Yes I know that you cannot have both top and bottom weight on the same ball. I was just making sure that on 10lb and up that You can have 3ounces either way and be legal is that correct. Thanks

Sorry about the triple post not sure how that happened