Joe--- If you want to send back the module or the whole kit for a refund, I won't be too upset...
Or, since a D M*g will let you use 3AAs side by side, if you want to trade the C module for the next T**K D cell module I build (it'll be a while though) we can do that (and I can build in a resistor if you want to do something weird as far as the battery configuration.
Or you can trade down and get some cash back for the SWAK D cell module I still have in stock, and have something to work with sooner, with still decent throw..... And more LUX / lumens than running your TXOK on Alkaline AAAs would produce.
Sorry this is so frustrating for you. Had I known what you wanted to do before you bought, I could have given you advice.
The 6AAAs in series - parallel is possible but impractical IMHO, and since AAAs are ~44MM in length rather than a C cells ~50mm you would have to take up some extra space with the holder, or use a spacer in a 2C tube or do a custom cutdown tube.... Actually, now that I think of it, the resistored insert I have is just about the right dimensions to make up the difference in a 2C. using a series parallel AAA battery pack.
Just for reference there is about a .180 in. / 4.5 MM difference in the depth of C & D heads... You can use a D sink with a spacer (and lose 30% of the heatsink mass) in a C head, but the reverse won't work.
I could have just built everything with D thickness (.280 inch) sinks and used spacers to put them in C heads, saving myself a lot of fairly expensive aluminum stock... Or even cheaper is to cut them out of 1/4 inch thick flat stock saving money and lots of lathe time and other hassles. But overdriving the Luxeons with direct drive on three cells I opted to go with as much mass as practical.... The larger the mass the slower it will be to heat up and the better it will dissipate heat... and heat is the greater enemy to Luxeons than current / voltage are IMHO.
Apparently, you want to stick with using primary batteries, ???? since you keep NOT commenting on my suggestions of LiIons, which would give you the best, most practical way to achieve the size of light you are wanting without wasting a lot of "lumen potential".