Having thought about it I dont think 1/2 in at the top will give me back the ride height so I am going to fit new springs as they are only $30 each ( £54 for two) and if the top pad is shot fit the 1/2 inch poly to compensate.I purchased a 1/2 in thick board for $3 ,put it on my anvil and wacked it with a 16oz hammer multiple times . Not a mark on it so I think its strong enough.
I have the spring compressors but will not do it until the spring ( ha ha joke) as its too wet and cold.