If you do put it in a vice, which is your best bet, cut up an old rubber car floor mat to protect your coilover from vice teeth. Try and get a hold of paraffin and use that as a lubricant, its a lot better than wd40. And obviously give it some gutty with a deadblow mallet. It should budge then If not then get the blowtorch out. When youre happy with the height give the threads a good paint in copper grease and you can even tie strap a bike tyre tube around them too.