Got mine on last week, as the suspension is slightly tired it has made a discernible difference and is allowing the Michelin PS4's to really dig in. Nice to have a low cost mod that actually has an effect.
Any claim will be recorded on the MIB database so needs to be declared for ALL insurances. If the Boxster is a second car consider what a claim would do to any other insured vehicles costs and weigh it up as a total.
Protected no claims just reduces the overall costs but you still have a claim so it will raise the premium.