i'll explain my thoughts and what i did with photos
this is a standard 12mm housing with heatink,i screwed the g2 lens barrel fully till the metal frame of the barrel make contact with gball's metal frame,i found out that focal lengh of the 1st lens doesn't matter at all as the colimated beam that exits the gball is perfect and very small in diameter on the first 2-3cm
this is the fully srewed barrer with the g2 on top of gball
this reverts the gball's focusing and you only have to use another lens and focus it as any other bare diode
this is the reverted output
after that i just used an empty m9x0.5 threaded barrel and screwed in a 3 element lens that i wanted(1 more standard 12mm modules could work also)
in front of it i screwed the sanwu's 3x beam expander adapter
by srewing in and out the front part you have a fully adjustable focus
and i always have the choice to stick the beam expander on it.
the only thing that have to worry is to have a very clean lens for the reverting beam part as the beam that exits the gball on this close distance is nearly perfectly focused and it burned a hole in the first lens after junk got in.
the diode runs very happy at 4.2A without any degradation with more that 10hours usage on it.