2 inch pipe will work great, and you won't have to worry about clogging. The fact that you already have it negates any increased cost over smaller diameter pipe.
As far as setup, that will work fine. You just want to make sure that if the filter pads get clogged, the water can overflow over the first baffle into the rest of the sump.
That's gonna be a LOT of seachem matrix... any reason you're using it over bioballs or pot scrubbies (my personal favorite)?
To properly set up a filter sock, you can actually buy a filter sock holder online:
Well the matrix was on sale and I like the idea of it, by august I should have the 58lbs of seachem pond matrix I ordered, went on backorder, costed me the same as the scrubbies or bioballs in the ammount I wanted.
If the pad gets clogged the water would just flow through the crate to the left.
Went to lfs and they had a similar mechanical filtration setup on a salt tank.
Thanks conner for the proper way to setup a filter sock. Ill probably modify a clothes hanger.
The crating is to add structural support and allow for water flow.