Chris – the only superheater I've made is to LBSC's design, for Tich.
It was not a success – mainly because the flue it's in got plugged the first day out, and I have not been able to clean it out – 20+ years without it has convinced me that the effort is not worth it. I've tried poking a 1/16th steel rod through, but no luck; the front end and superheater are just too cramped, at least in my build.
Now, I'm certain that a radiant superheater makes a big difference to water and coal consumption, as well as condensate on ones' glasses. It does make you worry about lubrication of cylinders, etc. The Raritan build (CI cylinders and rings) does NOT have a lubricator, so one less part to make or purchase. It is saturated, of course.
I think that what we need is for someone to make 3 or 4 locomotives identical locomotives, with the exception of superheaters and, superheater type. Then a valid comparison can be made. Say, a stud of Simplexes, with:
1) Simplex, no superheater;
2) Simplex, in-flue superheater;
3) Simplex, two-tube radiant superheater;
4) Simplex, coaxial superheater.
And, measurement tools for determining efficiency.
Me? Nope! I'm not going to build them! Life's too short; I've got my Shay (no superheater) to get running when the snow melts, my 2-8-2 (superheater removed by previous owner) to fix some leaking pipework, and get my Ivatt 2-6-0 running, which will be made without superheaters, just to get the thing on the rails. Mind you, I'd love to try all 4 Simplexes (Simplii?) one day, so hopefully someone'll get cracking and churn them out.
A fun and challenging hobby, and I enjoy the individualism shown by all – it would be boring if we all made the same thing, right?
John.