What exactly would the problem be in using the 0V - +5V range? Those are perfectly normal CV values, and by using the Disting, you're definitely up in that range going into the 2S. I'd say take the Disting's adder out of the patch and use the wider CV range, and just restrict the Marbles' behavior so that the amount of voltage swing is reduced but within the desired range of activity. Besides, it's a bit of a waste of what the Disting can/should be doing.