No worries! Consider the 2x123 sized body for the "3v" Mule head as well. 16650, 17670, 1xrcr 123 with a dummy spacer cell, 1x primary 123 with a dummy spacer cell, 1x17500 rcr with a spacer, the possibilities are more numerous than the 2xAA tube, it is correspondingly shorter than 2xAA but still fills the hand nicely.
those are some great ideas, you're the man! thank you!