This is from this year's rule book :
"18b/3 A bowler is using the two-handed approach. The bowler’s dominant hand is the right
hand. Can the bowler use the right hand for spares?
Yes, since both deliveries are with the same dominate hand, the bowler did not change
delivery and, therefore, is not in violation of any USBC rules"
As long as the ball is legal with both forms of delivery then it shouldn't be an issue. This means that you would use two different ways of measuring the static weights. One with the center grip at the bridge and the 3rd hole as a weight hole. And the other with the center of grip between the fingers and thumb hole(3rd hole). The 3rd hole would need to fall under all rules of a balance hole when bowling two fingers.
"2. One hole for balance purposes not to exceed 1¼ inches in diameter. This hole may not
exceed 1¼ inches at any point through the depth of the hole. (Slugs and tape will be
allowed, however interchangeable devices are not allowed)"