Coilovers advise needed please, Octavia vrs

I've put my facelift Octavia vrs on meister r coilovers and it doesn't go low enough, but I was going to fit shorter springs as the standard ones are quite long, but was wondering if I'd have to fit stiffer springs? My current ones are 170mm long and are 7kg/MM. I've seen some springs which will fit and are 120mm long, but should I stick with 7kg/mm

All help appreciated. Thanks