A perfect summary - I know from experience - I've tried and failed !!!
If you fit a 5C you cannot use the BA21 and scope rings.
If you fit a 5E sight then you can use the scope sight rings but you cannot use the safety.
The answer is - get hold of a 5E sight and make a new shortened safety (you cannot buy one - they are at least 10 shelves above rocking horse poo & hens teeth)