For flush bits I find larger diameter bits give better results (someone mentioned this so I tried it, they were right). I used to use nothing but 1/2" bits. Tried 3/8" spirals; worked OK, did give a cleaner edge on ply. A 1/4" spiral was pretty much a waste of time except for light duty in the Colt. A 1" flush bit (Amana) works real well for me on various materials (larger spiral is still better on ply). Live and learn.
Any sufficiently advanced technology is indistinguishable from magic.
- Arthur C. Clarke