I wanted to get some feet, but decided I would try out a set of hardware to mount my PrintrBro to a few pieces of MDF, Even though my prints were sticking good, there was a bit of warping, so these are probably not ideal for use as feet on their own. With that being said, once screwed in to the fiber board, this set up is pretty stout. Now I should be ready for my 600mm x axis extension (ok, maybe just 200-300mm).

Vitamins:
Two pieces of 1/2# MDF, cut 1' x 1'
4-6 #8 Washers
4-6 3/4" wood screws
Gorilla Glue (If you are glueing the link between the two rear pieces)

Tools:
Hex Alan wrench for the Printrbot M3 Screws
Some liquid nails and a caulk gun

Steps:

1. Print the parts, everything should fit (one at a time) on the 1405 stock 100 x 100 x 100 bed. I used PLA and Slic3r. Also note, there isn't a seperate STL for the right front foot, just import the left front STL and then use a mirror function in Repetier to to get the opposite parity.
2. Add the feet one at a time. Take off the existing M3 screw on the Printrbot for each. Add the foot and then screw in the same M3 screw (each existing screw has enough space to reach the nut without using a longer M3 screw).
   2A) If you want to use the link, it goes between the two rear feet. Bond with super glue but make sure there is a good fit between both rear corners.
3. Cut the MDF if needed. Adhrere two pieces together using liquid nails. Make sure they are square and then press them together until they are bonded (I was impatient and only waited about an hour, but waiting longer is probably advised.
4. Lay down your bot and then use wood screws and washers to secure the feet to the MDF. I only used 4, but you can double up on the front feet if you feel like it.

If you screw up the MDF, no sweat. A 2' x 4' sheet costs about $9.