Catalyst 9500s, Stackwise Virtual and Etherchannels to different switches.

Having a hard time finding info on the issues I'm having, and admittedly very new to Stackwise Virtual.

Switch 1 & 2 are 9500's sharing a functioning SVL link between them with two HundredGig links plus a dual-active-detection interface between the two switches. All looks good.

Switch 3 is an old Catalyst 4507. Switches 4 & 5 are Nexus 93180YC-EX's.

I need to create a 4gb etherchannel between the 9500's and the old 4507r (all interfaces dumbed down to 1GB because of the 4507r)

Also need two separate 50gig etherchannels between the 9500s and the Nexus switches, using 4 TwentyFiveGig ports - two on each Nexus, and two on each 9500.

In both cases, I am using ports on both 9500 chassis - two on each chassis.

Whether I use LACP active/active, or PAgP desirable/desirable, only one of the interfaces on each 9500 will participate in the etherchannel. The first interfaces to link up are active; but the 9500 stack will 'down' the ports which linked afterwards using PAgP, or 'suspend' them if the port-channel is defined with LACP.

Group Port-channel Protocol Ports ------+-------------+-----------+----------------------------------------------- 1 Po1(SU) PAgP Twe1/0/45(D) Twe1/0/47(P) Twe2/0/45(D) Twe2/0/47(P) 2 Po2(SU) LACP Twe1/0/37(s) Twe2/0/37(P) 3 Po3(SU) LACP Twe1/0/38(P) Twe2/0/38(s) 

...what am I missing? Even if the answer is "understanding of Stackwise." At least that would be a much-needed sanity check.