My bad - I had removed the size on the float column during my testing.
Works perfectly, but you have (obviously :-) ) to add both size and scale, Skipper generates this XML:
<column name="funky_float"
description="Propel2 Float Test"
type="Float" size="4"
required="true" scale="2"
/>
and Propel generates it correctly. So no need for changes to Skipper for this, but thank you for offering!