You really shouldn't have to use lye (sodium hydroxide) as it will make the emulsion too soft and delicate and easily damaged. You could add sodium metaborate (Kodalk) or sodium carbonate instead. A paper developer like Dektol which has hydroquinone in it will also increase contrast. Have you looked at Ilford's instructions for reversal processing? http://www.ilfordphoto.com/applications/page.asp?n=90