What hole size do people find suits best to fit 52mm Defis to a non drilled pod?....I know 52 could be the answer...but people may have found otherwise and left a bit of play for adjustment of absolute position for example....

 

Used a 50mm hole saw. That way if you get the alignment of the holes out a bit you can open them up gradually with a half-round file, increasing the hole sizes in the right direction to bring them all into line.

I found that even with very careful marking I was a little bit out when I drilled my ScoobyMania pod, but adjusting the position by filing let me get them absolutely bang on.

Probably obvious, but you really need someone to hold the pod down as you drill, and go v slowly. The torque off a drill bit with that many teeth is larger than you might expect.

 

Ah yes...torque!!!...thanks 50 sounds good as a start..