The puffing out of the chest isn't anything that will help you and IMO is not worth mentioning at all in court. What the court will be concerned with is simply the issue of whether you were, in fact, speeding. Your defense seems to be not that you weren't speeding (you've not said anything about what speed you think you were going and what evidence you have of that) but that you are trying to cast doubt on whether the cop can prove you were speeding. In order to make that kind of challenge, you need to know exactly how the cop measured your speed. Even if he used the word “paced” in conversation, that may not be exactly how he measured your speed. Might have been radar, or whatever. In any event, you need to know exactly how he determined your speed if you want to make this kind of defense. You ought to be able to get discovery to find that out.

If he properly determined your average speed over some stretch of road as 53 mph, then that indicates you were speeding since the speed limit was either 40 mph or 35 mph depending on the portion of road you were on. If you were slowing during the time he measured the speed, then if the average was 53 mph you must have been going faster than that at the start of the timing. The court if it accepts that the timing of 53 mph was accurate still find you guilty but just of going 53 mph in a 40 mph zone instead of 35 mph if your exact speed in the 35 mph portion cannot be determined. But in any event, you need to start with what the cop says he did to determine your speed.