Harvey, it should work with out the Incra inserts, but the only place for dust to go is thru the hole arond the bit. The smaller that is, the more the extra holes will help.
Some will tell you that under table DC is not needed, but if you are cutting dadoes, fence based DC is useless. For edge routing, good fence based will get most of the dust.
Many routers have dust collection adapters that work quite well, also. Still for edge routing in a table. fence DC probably is better. The inserts with holes would improve DC that way as well.
Over engineering? No. Do you need it? Depends on your use, and how effective DC you want!
Hope this helps make it clearer than mud!
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