Experience/advice on in tank sump?

I have acquired a 35g tank and I'm leaning towards a DIY internal sump for filtration.  Something like the video below.  Any thoughts on this?  Anyone doing this or done it in the past?  Any reason not to do it?  seems simple enough and something fun and unique.  I just like playing with different setups.

I like it because of how customizable the design could to be.  Obviously though, it's pretty locked in once you've made it.  One early thought was to not make it the full height of the aquarium, or even make it hang on the inside.  HOI?  lol.  Anyway, it seems like it could have the perks of a sump without the risks, though minimal, of external plumbing.  I just don't know if it would be so small as to not really be worth it.  Would probably be about 12"x12"x3-4"?

Ready, GO!

There isa. Couple things I may do different, but yeah this is a pretty cool build.