is mine a stupid idea or not?
sounds good, might take a lot of work and money to make happen though.
I like trying to "fill" the D size space with as many watt-hours as possible when thinking up a mag-mod.. dropping down to a C size in a D host kinda negates a lot of real-estate that could be in the form of power for runtime or output. Whenever possible, I like mods that use D cells in a D case, or a configuration of smaller cells that can be fit 3-4 abreast in the tube, to maximize power available.
8 C size NIMHs would be about 48-58 watt/hours
as apposed to...
6 D size NIMHs would be about 72-86 watt/hours
in a tri-bored 6D host...(doubt it exists, lol... but if it did)
15 17670 li-ions would be about 83-89 watt/hours
28 AA size NIMHs would be about 67-90 watt/hours
(all calculated before losses, estimated, but good comparison)
of the bunch I like the 6 D cells the best because it involves the easiest drop-in solution for power, no complicated packs with tons of resistance points or complications. Less cells means less to manage, easier diagnostic when things go wrong. And there are a lot of bulbs out there that could make good use of ~7.2V.