I think for a real handyman DIYer, anything acrylic would be fine. For a ghetto DIYer like me, I would feel safer going with softer plastics though. Also, as I mentioned previously, those lok-tite (or whatever) containers come squared, so you dont have to deal with the headache of any additional attachments, just cut a hole, stick the MJ pipe thru it, & seal with silicoln.
The reason I like the idea of the MJ being IN the canister, instead of in the tank, is simple... its just less crap in the tank.

Regarding the powerhead positioning, I am unsure. In the example I linked to, the guy says the water comes in the bottom & out the top. I suppose this would be better.... My ghetto science leads me to believe that with the way his is plumbed, it is exerting all the pressure thru the output tube, which is directly outside of the top of the container. If the action were reversed, it would be pushin the water into the container, & out of the pipe at the bottom... And to me that would put pressure on the canister, bowing the sides, compromising its integrity. But I dont know if thats the case.... If you went with solid acrylic, it would be less of a concern I suppose.