If you are using a stock jib and have drastically increased sail area of your main (with your new square toped sail), then you can expect your boats weather helm to have increased from its stock form. You have added sail area to the main, and by not adding the same percentile gain to the jib you have moved your CE aft on the rig.
I would find out what the mast rake recommendation is for a stock 5.2 and start moving it forward from there.
As far as noticing performance differences, a gps with a VMG function could come in handy. This is especially true if you get a steady wind (direction) condition.
Fire up the gps and turn the track log on. Point as high as you can without leaving the sweet spot on both tacks. Note the headings. Average the headings and project a way point 1000 miles up the center of the two tacks.
Now use the go to function to sail toward that way point and read your headings and VMG speeds. Then change the rake of the rig and do it all over again, including the establishment of the place to project the way point (to account for wind shifts between each test). Notice your speeds and and headings. Are they faster, closer to the wind? Watch your VMG as you tune the boat.
Do a few more tests, each time moving the rig farther forward or aftward. Make particular note of the point at which the boat begins to exhibit lee helm. You won't ever want to set the rig farther forward unless off course you were going to do a one way trip, downwind.
Now go home and download the track to your computer (BEFORE you save it in the gps, which will take away the speed readings). Analyze the data and pay particular attention to your tacking angles. This is where you will easily see how well you are pointing.
I sailed with a buddy once (Hi Steve!) who was having lee helm on one tack and neutral on the other. We were curious as to what the problem was. It turned out that a shroud was fouled with a trap line, causing said shroud to be short. The rig was farther aft on when the short wire was to weather than on the other tack. So on the tack were the rig was farther aft, we had less lee helm.
When I analyzed our track, I could see that we were pointing higher on one tack than on the other and our overall taking angle was not very good. After fixing the fouled wire and raking the mast back a bit, the boat sailed higher with more balance between tacks.
As an example of track analysis, I am attaching a picture of a track I made in August. (to view it, go to upper left of the screen and click on the attachment link under my name)
The yellow portion is an upwind beat from leaving the harbor, hardening up at the FLR6S marker light where I go from south bound to more south west. The wind is out of the west and I am on Starboard tack from the marina to a point where I make a right turn and tack to Port. That leg was 1.5 nMiles and I averaged about 8.5 knots.
Then I take off, about 110º away from the course I was on and eventually am able to bring her up to 100º from the Starboard tack. I hold this course for about 20 mins. and cover 3.1 nMiles.
Then I tack about 85º but must have been on a lift because I end up falling to about 100º. Then you see me drop off about 70º as I begin to reach back home.
In this picture you can see that the waves have an effect on my courses. The waves out of the Southwest are on my bows when I am on Starboard tack and they slow me. When tack to Port, my bows are pushed away from the wind by the waves, but my speed increses.
On the Starboard tack leg I went about 1.5 miles in 10 mins. On the Port tack I went about 3.1 mi. in 20 minutes.
