I have the OP's RMS supplied rear link system on my 70 GTX. I have only driven it 70 miles and decided to rewire it(another story) I liked the ride. I did NOT build the car to race so that level of performance is beyond what I am knowledgeable enough to comment. I like the idea of the independent shocks and the adjust ability of stiffness and ride ht, you don't get that with a stock leaf spring suspension.
Here is a pic and a few to follow