Coilover spring too short

I ahve my coilovers set to full height in the rear and yet i still only have about a half inch wheel gap in the rear on 17’s and koni yellows on the highest perch. My question is what would be the best solution- get a spacer bettween the coilover collar and the perch (have to be custom) get new springs made with the same rate just a bit longer(preferred option) or i spoke to a place that makes springs and they said that they could just re-set the spring i.e. stretch it, but wouldn’t this affect the spring rate? so if i wound them down the wheel would rub cos the spring is too soft? or will it be ok? i would like to lengthen the spring by 1 1/2 inches. Thanks.

getting longer springs would be the best way to solve your problem IMO. Here in the US, ground control sells various height, diameter and spring rate made by eibach.