Koetsu Rosewood Sig or other Koetsu on medium mass arms

Frank Kuzma is a very interesting guy. Here is an interview. It transfers to English during the interview.  https://www.youtube.com/watch?v=UWvXgfjEPoA
He will do and try just about anything, any type of tonearm, any type of turntable. The only thing I can think of that he does not do are MM cartridges. Like Frank Schroder some of his designs go a step further into the brilliant category like the 4 Point arms. He now makes a full air bearing turntable. Some of his designs violate his own principles, I guess out of his desire to meet market demands or keep the price down. The Stabi M is a fantastic turntable.

According to posts on this site Mark Baker offers some of the worst customer service of any equipment manufacturer which is sad because his arms are not bad.

Franc said via email... his arms are designed to work with the best low compliance cartridges. He certainly went further with a more technical explanation, but I didn't want to quote him word for word. He also brought my attention to a recent Dick Olsher review in TAS, which I had already read. Dick had the Rose Sig on my exact table and arm. The review wasn’t the best written, but he certainly liked the Rose Sig.

@fjn04 

I've set up a truckload of Koetsu's across the board from Blacks, Reds,  to the stone bodied on a range of arms. One point I would suggest you have a think about is where are you going with your front end.

There is a valid argument from my own experience that you would probably get a better outcome if you upgraded from the Reference 313 to the 4Point11 first if you can. This will give you a sustantially better outcome when you do buy a Koetsu - one that will last you for years.