I don't have the exact words to define a capped riser, but when you say capped riser the mid sixties Tamerlane, Kodiak Special, kodiak, Super Kodiak, and Temugin come to mind.
My understanding is that it was intended to place some weight on the backside of the bow, sort of like a built in stabilizer. I also have a theory that fins and bullets were popular on the late fifties cars and that the points were a carry over from them.