I use a pex manifold, but I use the expanded type fittings (pex-a) because my dad has the tool. Works really well. The trick to cutting slots is to have a really sharp blade.
I made one.. flowed like crap. i drilled holes instead of slits... go with slits. i got about 78% efficiency. easy to build.
I did a combo of pex crimp fittings and ss hose clamps so i could still take it apart partially to clean it if need be
I used pex for both my 5 and 10 gallon MLT, wasn't hard to put together. Made them both together in about an hour and a half with a pipe cutter and a Dremel to cut slits in it. I love it, dry fitted it for ease of cleaning and haven't had any problems.