Thats what is so good about this site Mark. You get various opinions that are worth exactly what you pay for them (mine included). There are so many variables that can effect your choice. I tend to run the coolest plug that makes the power and have some insurance in pocket. Others run the hottest they can looking for 1 HP (possibly) until that 90+ day and a little bad gas takes out a motor. We ran for years with 9's lead and trail with no problems. We made some changes that made a 10.5 better. The computer I sent you to run made best power with the 9's. Not a huge deal if what you have is working. Read the plug and see if it is breaking down. Good luck!!