Rudder stress fracture repair

basically with all the pressure on the rudder it is causing damaged to the back of my contender, i have fitted nuts and washer behind to try and spread the load however some cracks have appeared from the pintle moving outwards and are starting to get worryingly movable when the rudder is fitted and I'm worried the rudder could pull part of the back off if it takes a knock or even a rough sail. 

Got epoxy and plan to file a v into the cracks and drill the ends then epoxy, to get strength back in the rear before remounting pintle for the rudder is this the right thing to do? or will i need fibres as well?

any tips, ideas really would be appreciated as I need to fix this soon, as the back is weak and will only get worse.