This is the way!
The less precise you are when building the armour, especially when cutting the joining strips and finishing them, the more accurate your armour will look. I know it's hard for some people but in order to look like the troopers on screen, you have to build your armour the same way. You can still take great care and pay attention to what you are doing, but focus more on authenticity rather than ideally, and the end results will be much better in my opinion.
Another thing that most people focus on too much (and I think you have too) is sticking to the 15mm width on the strips on the arms and 20mm on the legs. It's common for the strips on the arms to be 20mm and the legs 25mm, and these sizes look better when you are a bigger guy.
Look at the strips on this guy. They look to be 18-20mm wide on both the biceps and forearms.