Here is what I did...
I purchased a Loos Guage and followed the instructions included with it. I found that by tensioning the upper shrouds and the forestay, I could get the desired tension without effecting rake, and more importantly, without running out of turnbuckle adjustment range on the forestay. In the process, I would take 3 or four half turns on each of the upper shrouds for every 2 half turns on the forestay, then measure the tension on each of the three stays.I found that the shrouds harden up faster than the forestay, and they were at the top of the measurement range by the time the forestay acheived the bottom of the range.Before you start, using your main halyard as a measuring tape, take a measurement to a fixed point (I used the top of my pedistal gaurd) and adjust so that it just reaches that point. Then as you make changes, you'll be able to tell how much you've changed the rake.Having said all that, I don't believe that changing the rake back and forth a few inches has much effect on weather helm, steering, etc. compared to other variables like balancing your main and jib.However, tightening up the rig makes a noticable difference in pointing ability because the jib is not falling off as much as before.Fair winds,Tom