The exhaust springs that come on the F23 you cannot safety wire which could cause them to fly thru your prop if they fail. Matt has springs available you can purchase that allow you to safety wire. They are 4.85 per spring + shipping (8 in total) part number 054.1. You can contact him at Matt at 419.585.7002 or rpe@bpsom.com (www.recpower.com)
If can order an exhaust spring tool off Amazon for cheap, I ordered: