This is what the kite looks like in operation. You will notice that the sail is billowed by the wind. This is one of the ways by which the kite achieves its good stability. The spars you will notice are bowed (braced) which adds even more stability. The amount of bracing depends on the wind conditions a little for light winds more for stronger winds. The bottom spar is always braced more than the top spar. The right photograph shows the safety flag below the kite with two high altitude jets heading for the USA. Pictures taken at range of about 60 to 80m, 200mm telephoto, hand held.
The problem of the flying line stretching more than the antenna has been overcome by the inclusion of a piece of elastic cord (Bungee Cord about 5mm or 1/4 inch) at the top end of the antenna. If this precaution is not included the copper wire of the antenna will break because of the tension applied by the kite. The flying line is capable of stretching much more than the antenna. There is constant friction caused by the stretch and contraction of the flying line therefore we must take a few more precautions to save wear and tear on the assembly. A few plastic rings secured with lark's head knots to the flying line this enables the antenna wire to slip easily through the nylon rings and the elastic cord simply takes up the slack. The arrangement as shown below completely cures this problem. The nylon rings are available from shops which supply curtain material. The elastic cord is available from ships chandlers. The best diameter is about 1/4 inch (5-6 mm). The correct length of elastic cord is approximately 1m for every 15m and the ring spacing should be about every 4 or 5 m.
I have had every slip ring broken when the kite was struck by a sudden squall. Upon inspection I discovered that the rings on this assembly were not made from nylon but inferior plastic which looked like nylon. Check very carefully. Nylon will bend plastic will shatter. If in any doubt use stainless split rings which are available from Angling shops.

The two knots as shown in the diagram (Fig .02) have proven to be the most satisfactory for kiting purposes. The Lark's Head Knot can be tied at any point along a length of cord. This is the knot used to attach the nylon rings to the flying line so that the antenna wire can be passed through them. The Blood Knot with quick release loop is an excellent knot. Take the time to learn how to tie it properly, it is a very secure knot which has the advantage that it weakens the line much less than other knots.

I have been asked, "How do you attach the rig to the antenna?."
Easy, just use a piece of stout copper wire and a terminal from a connector block. Bend the wire as shown above slide the antenna wire and the stout wire into the terminal and tighten. Wind the flying line round the wire as shown. It will not slip when it is under load. This system provides for easy adjustment of the antenna tension. Use a Crocodile Clip to attach the rig to this arrangement.

There are many different devices which can be used as a sky hook. Modified paint rollers or whatever you can lay your hands on. A ships chandler is a good source of suitable hooks. A pulley is the best as there is less friction on the line. Make sure that the pulley is big enough to allow the nylon antenna support rings to pass through. A butchers hook works very well.
Sometimes I fly this flag when I am DX'ing, It is not an official flag but it does help to show that the kite is being used for purposes other than sport flying. Light aircraft sometimes fly close to the kite and the flag provides extra visual warning of the kites presence. The size is about 2 feet (60 cm) by 6 feet (1.8 m) and it looks good. Any flag of your choice would do just make it big enough to be seen.