That overflow is definately easier than making your own. I personally don't like it though as you're not giving yourself and emerg drain. Having a Herbie or Bean Animal would be much safer. You only need make your own overflow box with glass and skin it with acrylic. Make the box outside the tank, take it into a shop and have them fab the skin for ya.
Using my Chaeto tank build as an example of glass breakage is not the best as the glass was only 2mm to start with. The glass on your 40 will be a min of 5mm. With that said, I still agree with using flexible lines. Spa Flex is great for removing vibrations but is still kinda ridgid. Vinyl hardens over time, needs to be cleaned out if you don't block light and, of course, you have hose clamps to deal with.
This is also personal preference. I bailed on flare nozzles last year and started using round nozzles. Sure you don't get the spread of the 'fan', but you also don't have to mess with twisting them exactly where you want them.
Lastly, having your returns in that drawing location will limit your ability to point them into the back corners. If you've never used the Ys before, go buy them before you make your final decision. You'll see what I mean.
It's your build
but what I meant yesterday is to have the returns right beside the box. This way you have more room to point one into the corner. Even better yet would be to have the returns coming out of the box sides. This would allow you to take the Ys out if you don't like having 4 nozzles.
I'll try to find you some pics.