That is fascinating data Trev.
I've been playing a lot with dynamos and regulators recently (largely inspired by the ability to do so conferred by Manormike's oh-so-excellent DVR2 regulators) and have come to broadly the same conclusions.
The theoretical max to be derived from one of these generators, without increasing the internal heat generated in the field, is close to 140 watts; but only at the cost of not-useful compromise. To get that, it takes a fine-wound field coil ('12v' in the vernacular) with a thick-wound (ie '6v' as per original), armature winding. To get the thing to cut-in point takes a handful of rpm - close to 2000 - and it won't be regulating properly until closer to 3000 rpm. Ergo not a lot of use in normal riding. And the output is theoretical - I haven't tried to measure it, as it's a noisy business holding throttles at 3000rpm plus in the shed.
However, the use of an original thick-wound armature and original field at '12v' does give around 80 watts reliably, at the cost of some heat having to be dissipated in the field after Cut-in rpm and before full regulation kicks in. This would load the field a lot on long-lkegged machines habitually driven between those rpm, especially in built-up areas. In fact, the internal load at those rpm can be more than the dynamo is rated to cope with, although they seem to work OK - I have been running one machine in that configuration for over 20 years with various regulators of the early electronic type, but now a DVR. No melt-downs despite the absence of current regulation, as in all these applications - fingers crossed for the next 20 years.
I have one original 6v set-up (on my A10) which is OK and supports a 35W halogen just fine as you'd expect.
And I have one machine in this experimental hybrid 'fine field thick armature' mode, which may be OK for the summer for a country boy who seldom rides in heavy traffic, but I'll have to swap the field coil back to original or get a fine-wound armature for the autumn, to get reasonable cut-in and regulation rpm. These dynamos also run with DVR2s.
My only whinge with the fine-wound fine-wound mix is that you are stuck with 60W nominal output obviously (but the big plus is you retain the original cut-in rpm). But it would support a 45/40W halogen OK as long as the magneto is retained of course.
All depends how badly we want lights for what we do. I unfortunately need them often, to the point that I regularly take something with an Alternator when in doubt.
I was interested a few weeks ago, talking to Gary at SRM when ordering up a fine-wound filed coil for the hybrid experiment, to learn they they are looking at ways of getting more out of the original E3L generators, presumably because they are finding people overload the '12v' 60 Watt set-up. They apparently want to try to find some extra oomph, but it's hard. I think I heard him say that they are also going to be, or are, stocking DVR2s - but not sure about that. I for one never cease to extol their merits - to the point of boring people to death. And that's having had mechanical regs, JG ones, Podtronics ones, you name it. The DVR2 is the best I've had yet.