NP231 Doubler

Has anyone seen this product or know anyone who has used this?

http://cgi.ebay.com/ebaymotors/Cree...005QQitemZ150089135065QQrdZ1QQsspagenameZWDVW

I am planning my build and I was originally planning on using the STaK 5.44:1 2-speed case. I am not sure of this now after reading the ordeal that Capt. Nemo is having with his t-case. I have considered the Atlas II 6:1, but the price is a turn off. I am also considering using a Klunv underdrive (4:1 or 2.7:1).

Any experience with Klunv would also be greatly appreciated.

I'm using that same one in my buildup, here's a small half-assed writeup I did about how it goes together:

http://www.jeepin.net/forum/showthread.php?t=30470&highlight=np231+machine