Fidelity Research FR-64x

@mulveling I have tried three different headshells with my Koetsu RSP and FR-64S (copper). Yamamoto HS-4 (carbon), Yamamoto HS-6 (titanium) and Ortofon LH-8000.  Of the three, I like the Ortofon the best in my system.  It has the right balance of detail without brightness, midrange beauty and bass extension. I use PASS XP-15/XP-10/XA30.5. 
I know that the RSP is different than the stone Koetsu (which I would love to hear!) but maybe you should give the Ortofon a try?

-Karl

@mulveling Well I guess you have no excuse not to try the LH-8000.  I admit I was surprised too about my preference. It’s one of those things that was subtle but I kept going back to the Ortofon headshell and ultimately that’s where the RSP sounded best and where it ended up staying.  
I was able to use the Yamamoto HS6 despite the mounting holes because I can adjust overhang with my table’s sliding magnetic armboard.  

I find it extremely difficult, with Koetsu, to see the cantilever well enough to adjust lateral angle at the null points.  I rely on the cartridge body sides assuming they are parallel to the cantilever. I know this is a compromise. Let us know if the SmarTractor allows you to visualize the cantilever on your Koetsu if you end up grabbing one.

-Karl