My original idea was to use the Knowle tool as it seemed the easiest way to go, but, in my guesstimation the V in the plastic axleguard is too wide and deep to allow a sufficient depth of hole to be drilled to satisfactorily support the use of the flangeless bearing, hence my use of waisted bearings.
I have tried unsuccessfully to upload a photo to show my finished article, so I hope my explanation will be sufficient.
Interestingly, since postulating my theory about these wagons on RMWeb, a few members have said that they have dropped AG wheelsets in without any modification and with an acceptable amount of slop. This either means I am too fussy about the amount of slop I will accept but is OK to others, or, I have had a couple of rogue wagons with excessive moulded holes, but in my opinion, without modification the axles are like a dick in a bucket.
As with all conversions try the simplest option first to see if it works for you before diving in and committing scalpel to plastic!