I just upgrade to a Clipper from an Asp and wanted to share a little tip that has been passed down to me from other friendly CMDR's. I either sold the parts or downgraded(ones that can't be sold outright) before trading in my Asp and it saved me over a mil and a quarter 
Hope this helps anyone else when deciding to trade in for another ship...
Hope this helps anyone else when deciding to trade in for another ship...