Kickstarting with adapter teaming (10Gb NICs)

I have a Dell PowerEdge R740xd with em1 and em2 as 10GB DACs, using the bnxt_en driver, and em3 and em4 as copper 1Gb NICs using tg3. The target OS is RHEL7.5.

I'm having real trouble getting Kickstart to set up an adapter team of em1 and em2 (using the "lacp" runner, as opposed to "roundrobin" or "activebackup", etc.). For the longest time I couldn't even install, as dracut would stop and then timeout, and I wasn't getting any information as to why. I believe this was down to a bad "network" line in the Kickstart configuration file for the server. After some editing I have a Kickstart file which causes the server to install, but it seems to install using em1 only (all of the IP details for the team get assigned to it 'correctly'), and without any trace of teaming in /etc/sysconfig/network-scripts/. I boot from a USB stick (sdc; sda and sdb are internal RAID volumes) for historical reasons.

The Kickstart syslinux.cfg:
[...]
label SERVER1
kernel vmlinuz
append initrd=initrd.img ks=hd:sdc1:/configs/SERVER1.cfg console=ttyS1,115200
[...]

The Kickstart file SERVER1.cfg:
[...]
network team=team0:em1,em2 --bootproto=static --ip=10.1.1.1 --netmask=255.255.255.0 --gateway=10.1.1.254 --nameserver=10.1.1.253 --activate --teamconfig='{\"runner\": {\"name\": \"lacp\", \"active\": true, \"fast_rate\": false, \"tx_hash\": [\"ip\"]}, \"link_watch\": {\"name\": \"ethtool\"}, \"ports\": {\"em1\": {}, \"em2\": {}}, \"tx_balancer\": { \"name\": \"basic\"}}'
network --hostname=SERVER1
[...]

What am I missing, please? I tried having "--device=link" in the Kickstart file, but that wasn't accepted as valid. As it is I have to set em1's port on one of the two FEX switches to accept non-LACP traffic to allow it to talk to the install media server, and then configure the teaming after installation. I was told you can set up teaming at install time, I just don't see how.

Please tell me where I'm going wrong (-:

Thank you,

Ben