slammed mx5 kid

its about 280mm, yes had it all set up at my local s**t fit i had been told about wim but i'm along way away. so what sort of ride height should i have?

well ive lowered my mk1 mx5 on gaz coilovers lowered by 65mm but starting to think this may be to much as the car is very unsettled, even at low speed can any one advise what a good high would be? but i do want it low. the car is mainly on the road but track every now and then.