The blue ones I have from Novae will fit inside the tail cap where the spring normal rest. There is a lip inside the tail cap where the spring sets. The lip is about a 1/8 or so deep and wider there than the rest of the tail cap hole. So the blue ones may fit a 1D without any other mods besides making the spring fit inside the tail cap. You can cut the bottom of the spring so that the diameter almost matches the hole in the tail cap or I think I have seen post where they did use a stock mag C spring. I dont know for sure the blue ones will work, just a guess. You will gain about a 1/8 inch or so. The green ones I have will not fit inside where the spring sits. They are a little bit wider on the bottom. It appears that they used a different pcb on the green ones. Could be that the pcb is on top of the battery. The green ones do not like much to have fit. I would assume that a dremel tool or some coarse sand paper would make quick work of this to allow them to fit. When I make A 1D I always cut the mag body to fit the 32650 rather than the normal D size. That way I dont have to mod the spring and most 18650's are close to the same length as the 32650's. So I can use either one with a adapter for the 18650.
The one's I have seen where unprotected. I just dont like the idea of running that big of a unprotected li-ion in a hefty mag tube. This is one solution that I came up with that may allow the batteries to vent through the switch and out the switch cover, just incase things go wrong. I do this mod to every mag I build now.
