For best results fillers should be applied to a roughed surface. This provides a tooth to help prevent seperation. Everything I've read about steering wheel repair states open the break into a V shape to increase the mating surface area. Yes that expands the width of the repaired area too so it looks like \_/
This profile would work as well but not as easy to create (_).
I have to imagine it would open again in the same place some day regardless how it is done. Nothing lasts forever. Good luck with it.