FFC Pro Top Cover Vent for 4in Hose

Remixing BrookTrout's great vent top. I mount my fan at the end of the vent hose, so I resized the mount holes and the through hole. There is a little bit of clean up on the fit (.5mm on one tab off) and some material usage optimization.

Fits this thingi: http://www.thingiverse.com/thing:759705 for a 4in hose.

Full kit: http://www.thingiverse.com/thing:1708681