These are the correct points to keep tight. Some feel the stock top caps are not strong enough and a aftermarket top cap is stronger. It stabilizes the upper shaft in the housing, theoretically lessening the likelihood of failure. Usually the L-hand prop turns in a direction to load the torque on the top cap. GLH actually broke the top cap. I have upgraded mine to Max Machine Worx top caps as I am turning 645 H.P. and over 600 ft/lb torque on a 10,400 boat (382 Formula). The are $400 each. Others to consider are Teague and Billet Marine.