First off I'm speaking from what I've read about these fuses not from experience. If you have a hot spring in your mod then you don't need a fuse. The fuse takes up battery space so your batts might not fit with it in or it can compress the spring too much. If the fuse fails then you have a potential bomb on your hands. I think the safest way to go would be to put a hot spring in your mod if you can and use IMR batteries like you're doing. With a hot spring, if you get a short the spring will collapse and disengage the battery shutting the mod off.