Filling a 3.5oz CO2 tank off of a 20oz?

[apoc4lypse]

This might be a silly idea, but would it be possible to fill a 3.5oz CO2 tank using a "bulk" 20oz, 12oz, or 9oz tank, by hanging the bulk tank upside down and trying to fill the 3.5oz that way?  It may not be practical depending on how well your field fills 3.5oz tanks, but it would probably come in handy for outlaw games.  If I did it I'd be using a proper scale etc. to get an exact fill.

[scphantom]

It could work, but you may not get a complete fill. I could see a partial fill coming out of it though. I would always recommend weighing to to be safe.

[warpathpd]

Walmart sells a 24oz CO2 tank. You could get an extra fill with a 24, assuming you had the proper filling station.