Mixed code version configurations to migrate to v11.6

I’ve got 2 F5s with different versions of code and different configurations. The code versions are v.10.2.4 and v11.6. The v10 box has approx. 100 VIPs and the v11 has approx. 400 VIPs. I need to combine the configurations and migrate them to separate v11.6 HA Pair F5s already setup and licensed.

What’s the best way to accomplish this task?

My thoughts.

1) Use UCS from the single v11 F5 and load to the new HA pair.

2) Migrate necessary Certs and Keys from v11 to new HA pair.

3) From v10 F5, take VIPs and relevant configuration items from bigip.conf file

4) Convert configuration items from v10 syntax to v11 syntax

5) Add the converted configuration items to new HA pair

6) Migrate necessary Certs and Keys from v10 to new HA pair.

I'm not sure if step 4 can be completed easily, if at all.

Any comments are welcome.