mag69,
How many guy wires? Sort of depends on how 'paranoid' you are, and how safe you want to be.
The base of a mast shouldn't move/bend. Put some kind of a 'stub' in the ground so that it will hold the base of the mast still. How deep and how long depends on the nature of the soil where you live. You probably have a better understanding of that part than I do (since I don't live there). If that stub is going to add height to the whole thing then it should be as least as strong as the base portion of the mast. More is better as far as strength goes. Unless the base of the mast is placed on something 'solid', it will gradually sink into the ground. Not really something to worry about unless you live in a swamp, right? How many guys you use and at what levels depends on the strength of the mast and it's better to be safe than sorry. I'm assuming the mast is made in 10 foot section, so, I'd put a set of three guys at each joint. The foot of each guy needs to be as firmly 'planted' as the base stub (actually, more so). Turnbuclkes and thimbles are nice, usually makes things easier to adjust.
Bailing wire makes for a lousy guy wire. You want something that's strong, and not stretchy. Another case where over-doing it is better than under doing it. (If it takes an anvil and hammer to bend the stuff you've probably gone too far). Guys shouldn't be loose, they need to be tight enough so that the mast doesn't 'shake', but not tight enough to bend/deform the mast.
Getting to sound sort of complicated? Not really, but just good common sense. Unless you're a 'government', it's always better to 'over do' than having to re-do later...
- 'Doc