If an aftermarket suspension was installed, it is therefore a modified vehicle that you have. In this context, it render the vehicle both a personal and public safety hazard (quoted from dept. of transport and automakers' eng. dept).
If there is no way for you/mechanic to scientifically match the geometry/alignment of the original suspension +
damping + preload characteristics, then the advice is to stay with recommended settings (factory). There are obviously some folks in the industry who can install and correctly dial those aftermarket springs on performance Porsche cars (few in fact) but finding one in your area could be tricky. Involves a lot more than just slamming some cool looking coil-overs lolll Needs adj links on each and every wheels + custom alignment + damping + preload dialing. Read not exactly easy to accomplish and less than cheap ~ if you are half-serious about an intelligent suspension set-up and safety.
If the intent is a every-day street vehicle and you have nobody who can 'genuinely' dial this Boxster better than Porsche can; my advice would be to rip off this mess and replace with recommended (stock or ROW M30).
Sorry to hear man. Roadster fun shouldn't start like that. Sure you and your 10/y son will sort it all tough
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