I personally top around the 4th or 5th node in veg. Im starting to do alot of lst so pretty much all of my training is during veg. Plus it gives the plant time to recoop before flowering which in return gives you less chance of popping nanners. IMO.

If your plant get top heavy during flower you can alway stake and tie it up so you dont have to worry about splitting. Plus once again less stress on the flowering plant. Just my 2 cents