Any service managers or ex service mangers?

It's funny reading all the post from the guys that have worked flat rate automotive shops, that was my world for 30 years before I moved to marine and it seems nothing has changed there. I'm actually taking my 2019 Ram in tomorrow to the dealer for a small warranty job, but honestly I don't know if they really took the time to properly diagnose it two weeks ago when they ordered the part or just guessed because it's easier and more profitable to do that on flat rate. If it wasn't for the warranty I wouldn't be there. As far as my shop goes, like I said it's marine so other than warranty work it's not flat other than a few simple services. I was really hoping to read here where someone was using a functional efficient plan, but it seems most are or were flops. I'm thinking a quarterly plan based on monthly hours but eliminating Dec, Jan, Feb, which are our slowest months in this very seasonal business. Or not at all, but as I said this isn't my sole decision, some people prefer to learn the hard way.