Joining the exhaust pipes in any way will reduce or eliminate the scavenging effect of having a split manifold. The front/rear alternating of exhaust pulses is really the only reason for having duals on an inline six, other than the eye candy appeal of the system. Ditto for dual or triple carbs!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!