Start with the mast square in relation to the front and rear beam.
you can do this simply by laying a straight edge on the 2 beams and use a builders square to check its squareness....
(don't forget to allow for the rear track that's on the rear beam
if you cant get a big enough square then simply make one, its not hard to do !!!
use the 3,4,5 method to make your square... the base should measure 3 units, the verticle should measure 4 units and the diagonal should measure 5 units
it wont matter if you use inches for your units or feet for your units or metres for your units..... so long as you use the same typical length of measurement it will always come out as a square.
Again..... don't forget to allow for the rear track that's on the rear beam
Once the mast is square in relation to the beams then you can make the minor adjustments forward or aft to get better pointing or reduce helm.
you can physically alter the rake whilst sailing too ya know, by moving ya butt forward or aft you are actually making the mast lean forward or back too..... the "ideal" place to sail a mozzie when ya on the wire and pointing hard is with your front foot on that front beam and ya back foot at the chainplate.... move slightly forward or aft from that starting point once you have things sorted a bit better.
we've all been guilty of over tightening a rig at some stage, but as I've learned a loose rig works better in most conditions.
In all reality we really only need enough tension on the rig to stop the mast from coming out of it's pivot, Ive actually had mine so loose that I almost managed to lever it out with a tyre lever and yep that was too loose !!!
A simple trick is to use a std ruler and measure the distance from the bridal ring to the forestays thimble, once you have a base measurement then you can lengthen that distance by a 1/2 an inch then go and test it, then another half n inch and test it some more..... once you have a measurement that's working then you can duplicate it each race day with ease.
I can tell you my measurement is 8.5", yet if I haul down on it I can get it down to 5.5", & it will come out of the mast pivot @ 9.5"...... that's MY measurement, obviously your bridal length and forestay length will be different and so will your measurements.
One big thing with excessive rig tension on older boats is the flex that comes into it, older boats have lost some of their ridgitity and as a result when you haul down too hard your actually pulling the hulls together at the bow to the point where your actually creating a snow-plough effect..... this aint fast !!!
Before I replaced Shy's decks I could easily get upwards of 50mm of movement at the bow tips just from old soft hulls, once the new decks were fitted this has been eliminated.
Another check point is the beam bolts that attach the hulls to the beams, if they are even slightly loose performance will fall away very quickly, twisting hulls alter rig tension in a big way.
that's what its called when a sail is over tightened and from what you are explain it sounds very much like a choked sail issue. Sails aren't like the throttle on a car, 'giving it more' doesn't make a boat go faster it actually slows it down
I cant explain this online but dare say someone here will have a pic of a sail from the back of the boat showing a clean sail and one where the sail has been choked by over hauling on the mainsheet..... I have a black texta mark on my mainsheet and I know when it comes out of the bottom block then I've overtightened the main and I'm choking the sail
Don't be frightened to ask others what they think of your sail shape, its a quick and easy way to see something you may not understand or are blind to and just because they sail a different boat doesn't mean they don't know shyte...... I've learned more from an RL24 sailor than many others although there is one mozzie sailor that has been a guru and a half when it comes to sail shaping, thanks to him I have that texta mark