I would never run lr attys at 6v. you will pop them fast.
I have run, before i knew the dangers, cr2s in the bb, but wouldnt do it now to save my life unless they are protected..
if you want to do 6v it is best to use the cr2s that are protected. they do not last long though. Probably an hour or so per charge if you are a heavy hitter. use reg or hv attys. I prefer HV attys at that voltage.
You would do best to get another mod to do 6v that takes the cr123a battys. much longer charge and safer imo.