Thanks guys. Got it sorted. Went with Simons advice re: using a shim. Used a piece of 3mm 3ply and sanded the 2 outer layers until I got to the right size then tapered it off to near nothing. I was worried leaving it in case it pulled down to one side and stressed the tongue and cracked it when clamping. Plus possibly upsetting the rake angle. Thanks again everyone and thanks again Simon for your advice..