im in the same dilema except my car has too many mods to ever get it on a multicar policy.
so for me the only option is two seperate policies and which ever way you do it, you WILL get anally raped for the policy with 0 NCB.
The system is incredibly unfair. You clearly have 6 years of claim free driving yet as you cant use the NCB, your experience counts for nothing and you will pay the same premium as someone with no experience.
yet you have an accident, you have to declare it on ALL policys and you will have a boosted premium on ALL your policies.
Plus NCB expires in 2 years yet claims are declarable for 5 years.....
the system is totally unfair and against the consumer.