Ramona said..
Light breezes ease off the backstay, this will make the sail fuller and give more power. As the breeze freshens harden up the backstay. There will always be some sag even with a tight backstay. The sailmaker cuts the sail to allow for this. Backstay is too tight when the heads door wont close! Keep a reasonable pressure on the backstay on the mooring too. Enough so that the mast is held fairly rigid. Most of the rigging damage is caused at the mooring.
With your wheel backstay tensioner there is probably a vernier along the thread with an arrow. Put markings on this after you work out what various tensions you need.
Totally agree. The original manual came with the Ranger 33, their advice was to tighten the backstay when sailing and slacken it off at rest - but didn't say how much. The toilet door strain gauge works well. the Ranger setup likes fairly slack rigging, almost slack lee shrouds when sailing hard. it must be a slightly bendy hull cos there is enough tension to stop pumping when at anchor, and that test is not a bad indication that the rig is set up OK.
A bit different setting up a fractional rig.
If Sam has badly worn furler forestay bushes the foil gets eccentric and that can make the first few roll hard to put in.