Parker 51 cap on a Wing Sung 601?

[Alcuin]

Hello everyone. 
 

I just received a steel Wing Sung 601, and it’s not exactly as I’d hoped. Among a few cosmetic defects, I’m also noticing that the cap is quite hard to remove, and feels very scratchy against the body. I really don’t like the feeling of taking the cap off. I’ve taken the cap off of Parker 51s before, and it was such a smooth nice motion with a nice click. 
 

So my question is this: has anyone used a Parker 51 cap on a Wing Sung 601? I’m afraid to try it out of risk of damaging my cap, but if someone has tried this and found success with it, I’d like to hear it. 

[HobbitLife]

Yes I’ve done it with no problem, though on a plastic 601, not a steel one. Don’t know if there is any difference. 

[IThinkIHaveAProblem]

My two flighter 601s also feel scratchy when removing them. Better now after some use. In my experience 601 and “51” caps are interchangeable.