Thought to take another stab at it before break time.
I complicated it a bit more for experimental reasons. I'm close but still no cigar.
010113 422105 44201 40845 spec.jpg
(^.)\s(.)\s(.)\s(.)\s(.*)
\2 \5
My result is 422105 spec.jpg
I have my extension but also the unwanted "spec" and the space before. It seems I needed to treat the word groups by identifying them by spaces. This link was also a great help RegExp basics: Removing characters from start/end of names
I hope I'm going in the right direction, logic, with the code I' using.
Bob