Is there a way to override SQL generated during rake:test:clone_structure?

I have two tables with ID columns that must be unsigned integers. When
I try to clone the database for testing, Rails misjudges these columns
as signed integers, and the test cannot proceed because this table
type does not accept a signed integer for these columns (Sphinx SE
document and body tables).

Is there a way to hook into the database cloning process and override
the generated SQL with the correct column type?