[TuRo]

I would put some masking tape on a set of thin nose pliers and place the end link round the pliers gently pushing the end link up as pliers widen a tad- then turn end link round and do again. This will gain you about 0.5 - 1mm in height at the the end and about .3mm to .6mm in the centre - it also has the benefit of making the end link tighter as the hole and spring bar will come in about 0.25mm closer to case. The result will look better as the end link will fill the gap much better. Do it very carefully and slowly tiny bit at a time.
Yes 380s are longer and deeper than 50s, but you can improve them (by doing above), or find a set of 55s but even these don't fill the gap as well 380s I have found. I just live with a tiny bit of lug end showing on a 6251/62510h on a 1675 as I think the look and comfort is great