I am not saying this is good or bad just asking the question.

That's extremely unsafe. I would never recommend having an open space under a load like that. With how much weight is pressing down, if that outrigger pad gives...

Looking at that photo the only 'real' issue that comes to mind is "if that boom comes down, you are almost certain the s**t will hit the fan".

where i started pumping this the only place to put the outrigger on rezy jobs.  the dirt is a service line trench packed by city workers after side walk.  in the 39m,  if i set 2 feet back so the ashfault gets a square hole,  i'm 4 - 5 feet short from the back wall.  curbs are the best place to put the outriggers some places.

i would do a few things different, like not put the foot on the wall of the curb and still put a couple 4x6 on the curb so the whole pad has something other then air under.  to each his own...a shitty blow out