G'day 87_botanist,
I haven't built one (yet) but feel this should be effective and suited for purpose.
I am contemplating supersizing this design and building it with two fans, filters etc. in a larger box, effectively doubling the size. I feel I need a larger working area and this should do the job quite well.
Let me know how you get on, whichever way you decide to move.
Peace & goodvibes,
Sam