Conid Kingsize Antwerpen - Montblanc 149 Nib swap issue

Anyone else had an issue with swapping a Montblanc 149 nib into a Conid Kingsize and the nib collar being a bit loose, or being able to be continually turned in the section? I used the BM149E collar from Flexible nib factory and dropped in an old 18C montblanc nib and ebonite feed.

Installing a MB139/149 nib in a Conid Kingsize should be no problem ,but you should re-use the original Conid feed.