Configuring a LAG between stacked 6000 and stacked 5000 switches

Hi,

I have:

2 x 6000 PowerConnect (PC) switches - stacked, let’s call these 6PC_Unit1 &
6PC_Unit2

2 x 5000 PC switches - stacked, let’s call these 5PC_Unit1 & 5PC_Unit2

These switches have multiple VLANS

I want to create a LAG between these switches.Please advise if I've got
anything wrong, but my plan is to do the procedure below.

On
6PC_Unit1 run:

1. 
   Sw(config#) Interface te1/0/1, te1/0/2, te1/0/1, te1/1/2 (select
   ports1 & 2 on both stack members)
2. 
   Sw(config-if#) channel-group 1 mode active (enable ports with LACP,
   dynamic)
3. 
   Show interfaces port-channel 1 (confirm interfaces are in the port
   channel)
4. 
   Interface port-channel 1
5. 
   Switchport mode trunk
6. Switchport trunk allowed vlan add 1,10,20,30 tagged
7. 
   switchport trunk allowed vlan add 10,30 tagged

Do the above procedure on 5PC_Unit1
(i.e. configure both stack members)

Connect the following cables up:

5PC_Unit1 port 1  to 6PC_Unit1 port 1

5PC_Unit1 port 2 to 6PC_Unit2 port 1

5PC_Unit2 port 1  to 6PC_Unit1 port 2

5PC_Unit2 port 2 to 6PC_Unit2 port  2

Effectively creating 4 links between 4
switches and 2 separate stacks. Would this be the correct procedure to follow?

Also, I’ve noticed a number of guides mention
setting the spanning tree mode of the port channel to portfast – however I’ve
also read this shouldn’t be used on inter switch links and SPT sees aggregate
links as a single link.

Please advise if this procedure is correct.

Thanks