This type of repair if done properly has a very good chance of never repeating. Firstly you must stop the split from progressing, to this end you should drill a very small hole the depth of the crack at the point where it has stopped so that is at the end of the crack heading further into the centre of fore end wood. I use a 1mm drill for the hole (any imperial drill close to this will be fine) this will stop the crack going any further. I have always used Epoxey slow setting adhesive rot this type of repair because it gives you plenty of time to get the adhesive into all of the places required it also gives you plenty of time for clean up and adjustment. For the crack heading for the knuckle joint end of the wood use dental floss to pull the adhesive into and through the crack, to get the adhesive into the crack on the other side of the hole my favourite too for this is an artist's pallet knife because they are extremely thin and flexible at the end so ideal for pushing glue into cracks also the finest gauges from an auto engine feeler gauge set works well for this. Finally try to close up the crack if you can by using strips of bicycle tyre innertube as a compression clamp so not marking the wood.
Hope things go well for you.
Ernie
