I'm guessing that the one you have in mind is the one that was on milweb earlier today for a couple of hours? Looked quite nice and a very good price, was getting qute tempted!
Assuming it is then from my limited knowledge this type all started off as Portee's and were then converted later on to towed. As a portee the unladen weight is 4 ton 9 cwt, laden is 4 ton 19 cwt.
A friend used to own both a portee and a predictor. The predictor we took over to France. Only two problems, no weather protection at all and nowhere to put any booze to bring back!:stop:
With the portee you do need to wrap up very warm! No matter how hot a day it is you will still need at least a fleece, very thick trousers and flying googles!:-D In the wet I'd suggest a wet suit!:-D:yay:
HTH
Ed