I have always used a press block to put them togather and never broken one pressing it. I DID however, cave in the final cap on a Churchill once! It was so thin that trying to press the clip & final retainer in place caved the whole end cap in.
I have only had one returned that I sold sold, but I have only sold four of them and one had been lost. The one that was returned, I was able to repair with some CA and it is still holding today. (As with my pens) I have personaly have broken three of the kits myself. One was dropped on the floor when my churchill got caught in my daughters hair. It fell just under three feet as I was in a chair. Once El-Grande was noticed when the cap was put on and it was loose (IE: pulled out) and the other El-Grande was noticed while using it.
Of the sold pens, 2 were gifts so I would dobut the owner would show the person that bought it for them, if they did it still might not of gotten back to me.
For me, until they change the style, I have discontinued the kit and gone to the Ligero. It has a better designed coupler. If I have an order and someone "has to have" the Churchill, I will raise the price to include the cost of a CSUSA kit which will be bought just for the nib coupler assy. I also like the fact that the final end is brass and not plastic. It's much more like the Churchill in that way.
Rich, you mention the clip final and the clip diameter. I just happen to have a Rhoidum Ligero kit on my desk and I grabbed my calipers to check the size on the Ligero.
Wish it was a better fit myself. If it was brass, I would turn it and re-powdercoat it.
Final cap: .600
Clip: .591
FWIW, I have no idea what the bushings are, nor do I care. I build to fit the hardware, not the bushing guides.