Caliburn O-Ring Ram with Tall Base
The bars that connect to the ram were floppy and would get mis-aligned leading to failure after sustained use. The mod has a taller base to add / improve the connection to the bars. basically more contact area for more support. It's not perfect but significantly more stable. Although it does shorten the ram's travel its at the end and not by very much <5 MM. Works great for me but YMMV.
Additionally I added ribs inside to strength the thin walls at the o-ring groove. I printed in ABS as Captain Slug suggested.
The aluminum o-ring ram is still superior but if you are in a rush or have spools of abs laying around, give it a try.