I'm still seeing gluing in a piece of dowel that'll be about 11.5 mm diameter then dilling it straight in the centre with 11mm as being a pretty risky avenue vs just using the posts the holes were originally intended for. Once the post bit into the quarter millimeter of dowel and glue that would be left it doesn't seem like that makes for a firm base.

I might need to do a dry run on some other wood to be convinced.