So here is my dilemma, I need 4 encoders and am tired of hacking so many gamepads. Groovy game has the eco-wiz for 25 but that puts me at 100 bucks before shipping which I don't like the sound of......
There aren't enough inputs for one of these guys or I would go with that. If I understand correctly it has 21 inputs? Degenatron's video says it has 22 but that is probably a typo. 22 is enough, 24 is preferable. 21 is not enough so ---steaming pile of meadow muffin---....
You're going to solder either way, only difference is the size of the pad.
The AVR video is from his earliest prototype before he changed a few things around for greater versatility IIRC.
Newer AVR Encoder and KADE firmwares are configured like this.
24 Pins
--------
20 Dedicated inputs (all of which are usable as shifted functions)
1 Hardware Button (HWB) input for "shifted" functions (like P1 Start on IPac or the Shazaaam! on KeyWiz)
1 Reset
1 5v supply
1 Ground
To make 22 inputs (20 dedicated, 2 shifted) with the current KADE firmware:
- Wire 18 dedicated inputs straight from button to input
- Wire the other two inputs (19, 20) "backward" with the COM terminal connected to the encoder input, the NO connected to ground and the NC terminal going to buttons 21 and 22.
- For Button 21 (shifted 19), connect the wires from the NC terminal on 19 and HWB using one diode on each line as shown in the diagram linked above.
- For Button 22 (shifted 20), connect the wires from the NC terminal on 20 and HWB using one diode on each line as shown in the diagram linked above.
NOTE: If you leave out the diodes, pressing button 21 will also give you 22 because they are both tied to HWB
To make 25 inputs using the older AVR firmware, wire the 8 joystick inputs like this and wire the other 12 inputs direct:

One easy way to make a removable harness like the Xin-Mo is to solder on two 12 pin headers and buy 6 of
these 4-pin pre-crimped .187" harnesses from Paradise along with a daisy chain.

Only wish the minimus was 22 inputs...I can make due with that. But 21?! You are just messing with me now 
You can have up to 40 inputs (20 dedicated, 20 shifted) with current KADE firmware.
You can have 25 inputs using the older AVR firmware if the joysticks are wired like above.
Nobody's messing with you -- follow the directions I posted and it will work.
LMK if you have any questions.
Scott
EDIT: Since other links to AVR sources were requested, try
here or
here.