Wow, somehow I managed to do it by multiplying by -1 (I'm not a math whizz so I'm more impressed by anyone this worked): GravTime > 0 ? (PlayerObject.Height/2)*-1 + (PlayerAnimations.Height/2)*1 : (PlayerObject.Height/2) - (PlayerAnimations.Height/2)
I used the conditional operator to test if gravity is inverted, and that puts the character the right way around! Now I just need to figure out the slight flinching frame bug when you first press down, it seems to go away after fiddling around with the keys after a moment, but I need to really pinpoint what's causing this, is it a graphical glitch or something funny with the pin?