There was quite an extensive write up on repairing a Stealh, I think it belonged to Davefarmer a frequent writer on this forum.

The dagger board case is the hardest repair of all and the quickest way of repairing these is to remove it completely from the hull and replace with a new one, no matter which way you seem to attempt a repair it will create a problem like not allowing the board to slot in. Stealth marine will sell you a dagger board case and its a simple matter of delaminating the original from its hard points in the hull and bonding the new one in ( making sure you expand the new one with a taped board in place ).

Look in the composite aircraft forums for tips on repair like putting in backers, using adjacent or the opposite hull for formers and chamfering the edges at 40:1 etc.

By any chance was it trailered on a conventional trailer with rollers on rather than carpeted cradles,I have seen similar damage to a Stealth by the hard rollers localising the load to much over rough roads, the rollers eventually completely punctured the hulls.
Best of luck