Yes, I get the part about the colletts being used with the short roses.
What has become clear today is the short roses with the later Mk 3 collet, # 06.6520, with the spherical washer should be used on all Belled pipes, balanced or unbalanced.
Short roses with Colletts # 06.3990 with steel or copper washer should be used on earlier/original square type (non belled) balanced pipes, these flanges have cut outs for the correct colletts.
Long roses with steel or copper washer should be used on unbalanced, square type (non belled) flanges.
It's the flange that determines the correct Rose/collett, not balanced or unbalanced.
Like I said, Good Stuff Dave and thanks......