MSTP with Juniper and Cisco Switch for load balancing

I am attempting to use MSTP to help with some load balancing and redudancy. I have two cisco access switches that feed into two EX4300 distrobution switches. If there is a better way to manage this please fee free to sugest this.

I would like to split off traffic by VLANs but still have the second EX switch in place for redundancy.  At this time the traffic is being re-routed in a simulated failure situation, but when all devices are working the Ciscos appear to be sending all traffic, regardless of VLAN to only one of the two Ex4300.  The closest documentation for this I've found is for 2 Cisco and 1 Juniper (page 12 http://www.juniper.net/us/en/local/pdf/implementation-guides/8010002-en.pdf).  When I look at the spanning tree on the Juniper switchs the correct switch is root for the correct MSTI/VLAN group. When I look at the spanning tree in the Cisco, all MST instances/ VLANs are tagged to the same juniper switch, leaving the other switch in standby.

As the real system has more VLANS and additional access cisco switchs, I have simplified this as an example. Not all VLANS in the ranges indicated are in use or part of the trunk ports either. There is no VLAN-1 in use on the network.

Simplefied line diagram:

                           |--------   EX4300-1  (traffic for VLANs 1-9) 

Cisco Switch --|                                                       |        (tunked connection between junipers)

                           |--------   EX4300-2  (traffice for VLAN 10-19)

Protocols Config from EX4300-1

protocols {
    lldp {
        interface all;
    }
    lldp-med {
        interface all;
    }
    igmp-snooping {
        vlan default;
    }
    mstp {
        configuration-name region1;
        bridge-priority 28k;
        interface left1 {
            mode point-to-point;
        }
        interface left2 {
            mode point-to-point;
        }
        msti 1 {
            bridge-priority 24k;
            vlan 1-9;
        }
        msti 2 {
            bridge-priority 28k;
            vlan 10-19;
        }
    }
}

Protocols Config from EX4300-2

protocols {
    lldp {
        interface all;
    }
    lldp-med {
        interface all;
    }
    igmp-snooping {
        vlan default;
    }
    mstp {
        configuration-name region1;
        bridge-priority 28k;
        interface left1 {
            mode point-to-point;
        }
        interface left2 {
            mode point-to-point;
        }
        msti 1 {
            bridge-priority 28k;
            vlan 1-9;
        }
        msti 2 {
            bridge-priority 24k;
            vlan 10-19;
        }
    }
}

Cisco spanning-tree Config

spanning-tree mode mst
spanning-tree extend system-id
spanning-tree pathcost method long
!
spanning-tree mst configuration
 instance 1 vlan 1-9
 instance 2 vlan 10-19