first build, first grow (help, I have the tendency to overthink shit)

Hello everyone! So excited to finally start! Been dreaming of doing this for years, and there was just always something in the way! But now I got a 4 by 8 tent with an Evo 8 in it, plan on having more grow sites eventually but starting off smaller until I can get another light, Just four totes.
So I'm building a rdwc system outta 27 gallon totes, idk if anyones seen the black and yellow totes from home Depot? But there's ridges on the side where it's a little raised, and I decided on 3in PVC so the bulkheads are big enough where they run into said ridges, which makes me think I won't get a good seal? Only four plant sites, and this is only an issue connecting the back two totes, there's a space in the very middle of the totes wide enough but the makes me think that the flow of water will be impeaded by the hole not being at the very back? If that makes sense...

Looking at where your bulkhead is I would not put it there. I would put it to that space to the left. It looks like it’ll sit flat against the surface, make sure those rubber gaskets are flush on the inside and outside so you don’t get leaks. Once your set up is complete, I recommend running a leak test on your system by loading it up with water and run the pumps for a few hours. That’s what I had to do with my new set up.

You're right, you won't get a good seal there.. Use the middle where you have room..

So everything works! No leaks went with the middle spot. I think I need a bigger water pump tho because it's not circulating at a good rate, flow seems lethargic I thought 800gph pump would be enough. I fucked up drilling the holes for the totes. The res was supposed to have the hole in the middle too but I put them at each end, had to get janky with the return