Youngest informed his insurance about lowering his car & they were OK as long as it was 50mm or less.
But, as has already been said, only YOUR insurance can tell you.
Some will be fine, others will throw a hissy fit.
Also bear in mind that insurance companies are constantly looking for ways out of paying up for repairs "you didn't declare that air freshener as a mod therefore..."
They're more than happy to take your cash now - but they may inspect your mod very closely if ever there was a time when you want them to pay out.