MODIFIED Olympus FP-1 Power Flash Grip w/ FP-50R Flash for ALMOST ANY OLYMPIC Camera, OMD E-5, PEN

Great post.

I didn't realize you use C cells in the grip to charge the flash.
I have some C cell adapters (you slide a AA battery into a C sized battery case) and use rechargeable AA instead of huge C cells.
http://www.amazon.com/C-sized-Adapter-Shells-AA-Battery/dp/B000855034

This grip is an ideal application.