For some history on the plane here's a quote from William Robison in a previous Duelist MkII thread:

"Some history. Dave Platt designed the Duellist 2/40, and in 1976 when he owned Dave Platt Models he produced a kit for the plane.

I don’t know the details, but he and Morton Tanger had a fight about one thing or another, Platt was forced out of DPM and Tanger took over. The Duellist stayed in production, Dave Platt Models became Pica, and the later kit plan for the Duellist showed Morton Tanger as the designer. This was a lie, but Tanger’s name stayed on the plan until the end of production.

After leaving DPM/Pica Dave Platt then redid the Duellist 2/40, made a lot of improvements, and RCM published the improved plane as the Duellist 2/40 Mk II. But it was plans only, no kit. A better airplane, but you had to gather up your own materials. The plan is still available. Pica never incorporated the improvements in the kit version.

Estes has now bought Cox, and the Cox division of Ests has bought the kit line of Pica from Morton Tanger. They have plans to produce the Duellist 2/40 as an ARF. According to the early information given, it should already have been on the market. I do not know the reason for the delay. When I spoke to Mike Fritz at Cox, he said their version was the exact design Pica had kitted, so it must be the early model, which we now call the “Mark I” plane.

At the same time Platt was doing the 2/40 Mk II he was thinking about a larger plane for 60 engines. He did build a single prototype, but never published plans.

A few years ago several of us on RCU, who also happened to be Duellist lovers, got together and decided to do the larger 60 size version for ourselves.

We had an open discussion in a thread on RCU about the design, and then started another thread inviting subscriptions to defray the development costs.

We started with the Duellist 2/40 Mk II, enlarged it by 25%, and made a very few other changes. The biggest alteration was converting to a two-piece wing. We retained all the proportions of the Mk II 2/40. We called it the “Super Duellist 2/60 Mk II.”

And yes, we paid a royalty to Dave Platt.

We packaged a total of 50 kits, there was also one set of the laser cut parts used as a proof of the drawings, Ernest Fleming, as far as I know, still has this set. Forty-nine were sold, kit serial number one was given to Dave Platt in appreciation.

At the end of our production all rights were assigned to Northeast Aerodynamics, they are close to the release of the Duellist 2/60. Originally they had intended to sell it as a kit, but with the market as it is they have decided to sell it as an ARF only.

If you want either version as a kit, there are still some 2/40 kits that come up on one of the auction sites now and then, and some 2/60 kits are still not built. Once in a while you will see one for sale.

So. Three other options. Buy the plan and build from that, or wait a while and pick either the 2/40 ARF from Estes/Cox or the 2/60 Mk II from NEAero."

I thought that was a pretty good summary!
Mike.