May I suggest maybe someone here that sells the Y Junction Box. Much more reliable then y cables. I believe Brian at http://9mileskid.com/
can make one, or Andrew Olson aoguitars.com.
Disclaimer: I make and sell Buffers. I also sometimes Modify, Build and sell preamps and amplifiers. My opinions are not intended to be sales pitches. I am a one man shop and prefer to spend time with my wife and family, i work full time on call and love to spend my spare time doing other things. I only make, modify or build things for those that seek them.