You don't have to use the 2 into 1 splitter box. You can use a dual pull throttle instead. I went this way and had custom made cables to allow for individual adjustment.
RR's Catnip Hill to Peoria ___Loopin' Seattle to WestFest
It started with some beers __1500 miles to the Dentist
Skeedaddle to Seattle______ A 30 year old on a Three Flags Run