Well after the little test I did at home I figured I'd do a little field testing of my UPS powered Studio strobes. So I packed up the family for a portrait in the park. While I didn't get the shot I wanted, it wasn't due to the strobes or the power supply. Using a 45" shoot through umbrella, I was able to keep up with the sun at 3/4 power and below @ anywhere from 10 to 15 feet from the subject, I never ran out of juice on this rather quick session (50-60 shots).
What didn't work were my crappy Cactus II triggers - they failed to fire about 30% of the time and my camera was never more 6' from the strobe at any time. I'm getting real sick of these things - gonna have to buy me some REAL triggers when money isn't so tight.
The faulty triggers lead to a lot of frustration in the family portrait (see Matthew, my youngest) since I was taking each shot on a timer, I'd have to run around the pond for each shot. Needless to say, running over there and then having the trigger fail really sucked. (you can see me in the picture about to through my hands up because I thought the strobe didn't fire) One thing I am going to order right after I finish this post is a remote trigger for my camera, this self-timer approach is for the birds....