First off, akfotog, I gotta say I love your work...
Is the negative really bad? Or are you just not getting detail that really is there?
If the negative is thin, I think you might have allowed the backlight to influence the meter reading when you gotta know you needed to ignore it and find a way to measure the light hitting the front of the Pony.
Did you take the two lights from the front and move them to the back? Or are they still there on the front? If the lights in the front didn't move then you would use 1.5 sec at f/22 still.
A gray card is a great way to do copy work. And there are plenty of folks here who know how to use meters that can troubleshoot your metering technique and offer helpful suggestions.