For ease of installation, I’d recommend a Triplanar VII. I use one on my Nantais Ref II Lenco and find it a good match. Effective length is 250mm; pivot-to-spindal is 233.4mm. Being a surface-mount, it requires only three screw holes to affix it to the armboard. You could probably re-use your current armboard if you really wanted--if you don’t mind the holes. And it comes with its own plastic P2S jig (which I have not used, as I have the Unitractor/Unipivot system). I can't say whether it would sound better than your OL arm but it would be more adjustable.
I also use an SME M2-12R but it’s much more difficult to install, requiring an oblong post hole for the SME slide mount. Good 12-in arm on the Lenco, though, especially if you want to use SPUs.
I also use an SME M2-12R but it’s much more difficult to install, requiring an oblong post hole for the SME slide mount. Good 12-in arm on the Lenco, though, especially if you want to use SPUs.