I also reckon best to have them, as it may(or may not) just be that if the gears the clips retain are not in the correct spot, it could be the cause of the problem- maybe not the worn bush, but slightly ineffective gear meshing (hard to find neutral- ?).
I wouldn't bother with deepening the notch any, that could create a whole other bucket of crap...
Also if you have a bush made, don't forget the oil scroll inside.
A mate made mine, but didn't have the correct gearing to do the scroll on the lathe, and while I was doing that by hand, (as an aside) put some thought into the direction of the scroll and whether it draws oil in to the bush in conjunction with the feed hole above bush top, through the scroll to be pumped up the shaft, or just fed via the feed hole, to be squeezed out the scroll (and up the shaft by the centrifuge action exiting through the three holes in the shaft)...?... any thoughts...?
How do the rest of the bits look..? Not hard to do, is it...?