My hunting selfbows are in the 140-160 fps range. I don' t know about a minimum " speed" per se; I like to just shoot the most bow weight I can handle comfortably and match my equipment accordingly.

Sort of a side note, but I snap shot a doe one year from half-draw with a 65# selfbow. I don' t know if the arrow even left the bow at 100 fps, yet the deer went down in 25 yds and died as fast or faster than deer I' ve shot with 250+ fps compounds. [X(]