flat-top vs flat-topped

flat-top and flat-topped both are adjectives.

Word	Noun	Adjective	Verb	Adverb
flat-top	No	Yes	No	No
flat-topped	No	Yes	No	No

As adjectives, flat-top and flat-topped are synonyms defined as:

flat-top (adjective)	flat-topped (adjective)
having a flat or flattened upper surface	having a flat or flattened upper surface