Rear coilovers for a skoda felicia pickup??

Hello! I have fitted Ford Focus mk1 coilovers on the front of my skoda felicia pickup, after some grinding they really well, but what about the rears? The springs that come with the focus kit are waaaaaay to short to use on the skoda. Even with the adjuster collar att full height the spring is still really loose. Is there a solution to this? I am thinking about just chopping the stock springs for now, how much can you cut of them before they become loose in the spring seat?

Thanks!