What do you mean by too much thumb weight?

Do you mean up to the legal limit of 1oz. or over that?

In any case, now a days, static weights are only meant to keep the ball within the legal confines as defined by the USBC, not really to regulate how a ball rolls.

In principle, however, thumb and negative weight make a ball roll earlier and finish with less of a snap, whereas finger and positive weight provide length and backend reaction.

But with today's high tech equipment, other factors take precedence over static weights, such as cover stock, core, mass bias and specific layouts (configured by your neighborhood, friendly and knowledgeable pro shop operator) that enhance these features.

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Regards,
BowlingWolf