Replying to Cutting down skis

okay so i managed to get some oldschool zag bigs at the local tip for a tenner (very strange as i live in SW England) and wanted to turn them into a chill touring set-up as they'd be like ideal. the issue is though that they're 188 which is just too long to be manageable for touring for me. anyone had any experience trimming down/reshaping skis? They have a fairly large amount of early rise so that may make life easier, but looking to take about 5cm off them.