Your style for the slimlines is good Bob, and the finish is good also, so nothing to worry about there ... Regarding the breakage i would bet it was due to the inside of the tube carrying some residue from the CA used, so when you came to fit the mechanism it caused the plastic to crack under pressure. When using CA with any kit it is important to keep the glue away from the inside of the tube. I normally use a potato to block the inside of the tube which has served me well over the years ...
The transfer punches that Brian mentions are very good indeed for the dismantling of kits ... 