Okay, I'm going to have to make a few points here, so bear with me
-It is nearly impossible to make a deduction-free cast that goes to handstand without leaning. I've tried.
-Most people end their kip in a support position. This is wrong. You have to end in a piked position, with your chest leaned over the bar, shoulders shrugged up, and toes in front of the bar.
-The mistake that most people make on their straddle casts, is that they simply arch up to their handstands, just with their legs apart. This is wrong, and you will be counted for a straight cast with legs apart.
-The sequence for a good straddle cast goes like this:
~Lean over the bar, with toes in front of the bar, shoulders shrugged, and chest leaned over
~Cast nice and hollow to about horizontal
~Push down on the bar with a nice hollow upper back. Try to stay leaned over the bar
~When you push down, shove your butt up into the air while separating your legs into a straddle. The straddle doesn't need to be very large. Try to do this while staying hollow
~Push until your body is in handstand, THEN close your legs
I tried straddle cast handstands for months the wrong way. After I tried this technique, it took me two days to get it to handstand consistently and clean. Persistence pays off! Try to get a light spot for the first few times you do this. It is a bit harder, and you will need to be strong at first. But since you are close to handstand already, I think that you'll get there easily. Good luck!
-Lauren