Seatbelt ticket
I'm not sure most officer know if the rule applies to the detachable belts, it was written to keep people from putting the shoulder belt behind them or under their arm. I'm not sure the intent was to include these rigid detachable shoulder belts. Bottom line keep it stowed (or removed) and you shouldn't have a problem.
Most people I know that have racing harnesses in their cars do not put it all on when on the street, they just use the lap belt. But they way the law is written you must use it all.
I have been wearing seat belt my entire life even prior to the law (1986 in California).
I have been getting conflicting information from the CHP and others on cars not originally equipped with belts, when the use of belts law was introduced in 1986 there was clearly an exemption for car not originally equipped, specified by year, this exemption is no longer in the current California Vehicle Code.
Alan