I considered doing this conversion with the Sopwith Camel (1/12 scale = 28 inch span). The kit says that it is roomy enough for "simple RC equipment" and in fact with modern mini sized stuff you could probably put the full set of controls in, if you used LiPo cells. I ran a bunch of calculations on MotoCalc with this airframe, and found that it was probably marginal, however. The program suggested that you pretty much had to use a powerful brushless outrunner motor on it to get a decently wide flying envelope.

What really put me off the idea was talking it over with a couple of LHS people, whose advice was to leave the Guillows kits for what they were designed for - display, CL or FF. They really didn't think that the conversion was worthwhile. I don't know that it is impossible, but you can probably find a kit designed for electric that would work better.