Not sure if this has come up as a topic before, but a thought on the rain-cap. I currently own a SO 8-man tipi with large Ti stove, and have previously owned a Kifaru 4-man and SO 6-man tipi, all with stoves. (Still to try out my new LBO base/tarp/base with stove jack in the tarp and one LBO, but thats a story for a different time...) I've never used a rain-cap, and have not yet - touch wood - had any problem with spark-holes in my tents. ON rare occasions I have had the odd bit of rain falling into the stove when cold (when its going that's not a problem!), but that has never been a big deal.
I can see a "theoretical" problem with the rain-cap. That is, any sparks that make it past the spark guard in the stove - and there will always be some - tend to rise rapidly on the column of hot air above the stove pipe, where it cools and dissipates beyond the tipi when they return to earth. However, stick a rain-cap on the top of the pipe and there seems to be a much greater chance of the still-hot spark bouncing back off the rain-cap, straight back onto the tent. It's basic science
Any thoughts?