re: earthing.
When there is a strike, the current will flow through ALL that is metallic in the tower in an iinstant.
The ammount of current in each part of the structure will be determined the the impedance of that particular path. The lowest impedance paths will carry the highest currents.
Therefore my advice to to run an earth of large csa as directly as you can up the centre of the tower.
It is inevitable that some currents will flow through the tower legs themselves, lets face it in terms of impedance galvanised steel is going to be a worse conductor than 35mm squared copper. But at the end of the day the currents involved in a direct hit excede the current carrying capacity of 35mm squared copper anyway.
So we have to accept that some proportion of currents will flow through the structure.
If you can accept that then you have to make sure that the currents flowing through the tower structure which will in turn heat up joints of high impedance in a flash.. You need to assure yourself that the joints of the structure dont rupture in the heat.
Soldered joints are likely to melt, a concrete base without the conductive additives will heat up so fast that the concrete base could explode or crack.
The guys if used for dissipation are intended in the main to distribute the harmful currents above the cabin or control room below.. Better that the currents travel above out of harms way, than develop high voltage gradients across the floor of the cabin.
The lightning strike will when it touches ground dissipate through the earth at the speed of light.. Thus because of the natural impedance of the ground there will be a voltage gradient at various points in the ground as the current dissipates. Hundreds of volts may develop between points spaced just meters appart in the ground moving outwards from the base of the tower.
Dissipating currents by the use of guys may help to reduce the voltage gradient in the ground. But good enginneering must be observed in the use of guys, since harmful currents of a few thousand amps will heat up bad joints to the point that the guy wire itself could break.. If you then loose a couple of guys and its a windy night, you ,may loose the tower altogether.
If you choose to use the guys as an aid to distributing the currents, you must take the earths to each guy ring and run them directly back to the base. The frictional joint of a guy ring wont cope with the current and so it needs a tap across it of flexible braid (high csa) to a rod or earth ring around the guy base.
If you need more help with this subject I will be able to steer you in the direction of proper engineering guidlines for commercial towers.