That would give the pitch away, if one throws everything else 3/4 but drops to sidearm for the splitter, and the batters, if they're quick on the trigger, can make the adjustment. You have to throw EVERYTHING with the same arm motion and the same arm speed.
The slider---ah, the slider. Back in the day, when I pitched, I was a sidearmer all the way, and when I learned the slider it became my best pitch. My pitching coach---you might remember him, his name was Ed Lopat and he was a member of the Yankees' Big Three rotation from 1948 to the middle of 1955---showed me how to throw a good one, and I worked around with it and I had myself a devastating strikeout pitch. And by the way---have you investigated the crossfire yet? That's a move that works only with the sidearm delivery, and I fell in love with it and used it extensively, which further discombooberated the hitters. I remember one day when Lopat was helping me with the circle change, and he said to me, "I know you're going to crossfire it. You use that move with everything you throw." And indeed that move will work with any pitch. Check it out. :baseballpitcher: