Protecting yourselves and Insurance
The Combined Single Limit approach is better for protecting the Pilot, or his Estate, from pax and third party claims.
There are minimum insurance limits imposed by EU law - enter the reg of a UK aircraft into G-INFO and see them displayed.
I have a £7m+ CSL when flying, which for 4 pax seats in a turbine helicopter could easily fall short of the mark in the event of multiple death or catastrophic injuries. Were i routinely flying 5 up, then I would seek top up cover - known as Risk Excess.
Interestingly, in the US, there are no minimum insurance requirements in GA private flying, and the insurers rarely provide more than $100k per seat of liability cover. That may partially explain why more product liability claims are brought - the so called deep pocket theory.
Also, so-called disclaimers are rarely valid in the GA sector.