RE: Getting off and back on 'the line'; size
I'll do my best to answer these.
1) Yes, you will be deducted points as you are not holding the line. This would fall under the 1pt per 15 degrees. Also, if you were coming in too much, it would make the maneuver at the end very difficult as you would be "shriking" the box.
2) Once you exit the box you can do ANYTHING you want to turn around. If you need to move way in or out, a 180 degree horizontal turn can be the best method. If you are close to your line the 1/2 reverse cuban works well to position yourself, just adjust your postion on the way up or down with some rudder. The one thing I NEVER recommend as a turn around is a 1/2 cuban eight. This REALLY shrinks the time you hav eto get set for your next maneuver as you will end up much closer to center than when you start, whereas the 1/2 reverse the opposite is true. When you are out of the box, take the time to get EXACTLY where you want to be, wings level at the altitude you want so that you arent at a disadvantage when you enter the box.
3) You can fly as low as you want. HOWEVER, it took a LONG time, but I finally learned my lesson. I used to LOVE to fly low, and when you do it right, it looks great. However, minor altitude changes are MUCH easier to detect low. For example. If you do a slow roll 10' off the deck, and you lose 3' of altitude, it is VERY obvious. If you do the same thing at 100', it is almost inperceptible. So, the moral is, fly at a higher base altitude. This also gets you out of a lot of turbulance problems low. 100 - 150' are good base altitudes.
4) As long as the radii are consistent, it doenst matter how tight or lose you make them. Remember though, pulls at the top are MUCH easier to make tighter than the ones at the bottom as you have gravity helping, so you need to be careful with this. Most people doing a square loop with make big radii at the bottom, but seem to always make tight ones at the top, even though they are pulling the same amount of elevator, because your speed is usually reduced and gravity is helping.
Hope this helps,
Arch