BTW is there any specific retainer which works the best for holding the springs.
I know I had one which was perfect and another one which was not that good but canīt remember which was which.
Long time gone since I build my cars or replaced a spring.
From what I remember I had the old CRC metal one the CRC plastic and the 12R5 retainer.

I think one of them was easy to replace a spring and hold perfectly.