Additional Details

"G.Thun" has the simplest design for building even at home... Anyone who can weld thin wall tubes and sew fabric could repeat the "G.Thun". Under the link Sketches I put the real drawings in some scale. With the pointed dimensions I think the scale is not the problem.
Being afraid to be impudent I would take courage saying that "G.Thun" meets almost all the requirements mentioned for winter commuter, sophisticated trike designs and sociable vehicle.
The delta scheme design (1fr 2rr) has many advantages and the only disadvantage is its low stability on high speed cornering. On the straight part of the road you can drive on up to100 km/h but on cornering the speed should be thrown down: the sharper corner the lower speed. But even on the car if you love your tires and bearings you do so! Much helps the deviation of the rider's body to the side of cornering.
The prototype of "G.Thun" weights 22 kg. That is because I took the tubes for frame (7.5kg) with thicker wall than needed (I do not have TIG welding). Besides I put the heavy duty components from the free style bike (forks, rims, hubs, 48 spokes, and triple crankset - all steel).
The seat is made up of two strong belts and tissue covering with semi-hard elastic pad and weights 1.2 kg with tubes.
The steering mechanism consists of two U-shaped wheel levers, rod, two disks and two cables.
Full fairing is made up of fabric pulled upon the tube frame. For inside ventilation fabric should be transparent for air with the density that is function of climate e. g. for hot Israeli climate it could be a mesh. Such fairing is the lightest (all fairing weights 2.3 kg) and protects pretty well from wind and rain because its fabric is tight as on umbrella.
Frame of fairing is made up of 5/8" aluminum or 3/4" PVC hard tubes. Middle part of fairing with big (1m.sq) windscreen is attached between front and upper rear parts by means of zip-fasteners more convenient separated. Windscreen could be made of 0.2 mm PVC film but Dacron (polyethyleneterephtalat) is better (the one that is used for windsurfing sails). On both sides the windscreen could be rolled up more or less to make opens for fresh air. Besides, the middle part or only the windscreen could be removed and upper part could be put down on the rear rack so you can ride as on a cabriolet.
The floor of fairing with the capote on front wheel and crankset with chain are made of 1/8" plastic hollow cardboard.
Thus full fairing of "G.Thun" weights not more than 25 kg (55 lb.).
Because it is not for racing the weight is not critical. More important is to have power assist for climbing uphill. Now I am working hard on an electric drive and ready to donate 8-10 kg (not more) to have power assist of 200W for climbing 10% uphill 40-50km with 10-12 km/h speed.
As sociable vehicle "G.Thun" has four wheels. Now I uploaded two sketches for two-seater "G.Thun".

Any comments would be appreciated.