Vt75 tends to get hot near the bottom plate where we insert the battery. And if you use slight longer 26650 like the pink brillipower or something (cant rmb the name). The bottom plate seems to get slightly separated from the body of the mod, hence leaving like a gap there.

And yes as someone said about firing above 40w. I fire around 58watts usually and always get weak battery notice. My battery is 5000mah tho hahaha