Long story short, a rain shower (moving south) split the first turn area.  I wanted the distance due to the undercalled 2.5 hour MAT (with showers limiting the final southern turn area) so I went to the left (downwind) side expecting better lift.  This was some risk as the majority of the course and the cu field was right, but this would cost almost all the available distance for the first turn area.  Unfortunately something changed as I committed to the left of the rain shower and the good clouds decayed rapidly leaving me only one option, press forward for the back side sun.  I reached the back clouds at roughly 500 agl but the gamble worked and the thermal was 3.1 knots for 3500 feet.  Lucky, but I had the distance and was able to nearly max the larger second turn area and get back on time.  Won the day!