Can I get more out of my Koetsu ?

Thanks everyone, enjoying the discussion. @mulveling you have offered SUT advice previously and I am really happy with the difference in sound sound the MC4 has made. I kept the interconnect short as you suggested and will try out some shorter interconnects from TT > SUT also (currently 1M).

I have a good used high end HiFi warehouse at the end of my street so if I see any of the mentioned gear from this thread come through I will ask for a loan to experiment. 
 

I have been drooling over some turntables that could be possible upgrades but I think I am getting into the 10k territory which is allot for me and I might like to end up with something with 2 tone arms if spending that much. 
 

anywah appreciate all the comments and insights 🙏

For what it’s worth, I am using a custom built, solid state current driven head amp in front of my tube phono stage with MM levels of gain. The results are impeccable, terrific. I love it. I did it because you have to go out of your way for gain if you are using an Ortofon MC 2000 cartridge, which has possibly the lowest voltage output of any cartridge ever marketed but produces decent current output owing to its very low internal resistance (2 ohms). And I don’t own a SUT. this type of head amp is real competition for any step up transformer.

Kudos to Sutherland for going commercial with the idea, if that’s what they’ve done. Because I can’t find such a product on their website.

@lewm I ordered a set of head shell bolts designed for the purpose of experimenting with adding mass, like you said. The heaviest are about 6g so the difference = + 5g. My counter weight wasn't heavy enough to counter this much additional weight so I got a roll of solder I had lying around and tightly coiled it around my counter weight followed by some electrical tape then another layer of tightly coiled solder and more electrical tape. Looks quite neat and added enough weight to counter the new head shell screws. Do you see any issue with this counter weight hack?

After making this change I don't think there was a sonic improvement. I actually think what i was hearing was a decrease of airiness and less decay details. Kind of made the sound feel a bit dense and dead to me. (excuse my non audiophile language).
I replaced the 6g (total) screws with the 3g (total) screws and left the counter weight as is is with all the solder attached. So this added 2g mass above the head shell compared to my starting point + whatever the solder/counterweight calculation would amount to. 
I feel like the sound improved and had more of what I noticed was missing from the higher mass setup.

I will continue to experiment but just wanted to let you know that I am enjoying following your suggestions to see where it takes me. 

In my experience, mass itself isn't really the key factor in getting Koetsu to sing. I've heard them perform very well even on the relatively lightweight VPI 3D arm (*with dual pivot). I think the arm's bearing and overall energy management is more important than the moving mass, at least unless you're egregiously outside of the ideal 8 - 12 Hz resonance range.

Experimenting with head shells is fine and could be a good idea, but I certainly wouldn't bother with hacking the counterweight or tacking extra mass onto ane existing headshell. So I'm not too surprised the extra mass wasn't an improvement. The Koetsu body already provides a lot of mass itself (10 - 13 grams).

@mulveling - I think you are right. The less compliant cantilever is going to send energy back into the arm. Those old school Fidelity Research arms could handle it, not just because of mass at the headshell but because they were pretty substantial overall.

 I've done very well using the Airline arm- pretty low vertical mass, not a long arm tube (but a substantial one) and the overall horizontal mass of the arm carriage is huge. A damped arm might be able to accommodate this energy- though I'd be pretty careful about overdamping. I know somebody who uses a Coralstone on a Well-Tempered arm (not sure which generation) with success.