How would you phrase: "apologize if this is too obvious" without implying the person is a idiot? Example: BTW, don't waste too much time trying to put a round peg into a square hole -pardon me if that's too obvious (Assume to some people this may not be obvious -but I'm not sure so I really need to point it out.)

I'm emailing a guy about a computer program and I need to remind him of something that is easily overlooked but might seem offensive if I point out this step.