You need to go for polybushes that have a lower shore rating. The ones that 3GE used to sell where hard and almost like nylon, the ones that Rally design sell are softer to the point that you can move them with your fingers. The crush tubes will need triming by 2mm easy enough if there is some one handy with a lathe. Don't be tempted to try and use a hacksaw or grinder as they will be fit for the bin.
http://www.rallydesign.co.uk/product...ducts_id=11836