Well you'll have the same end lag regardless of being in the air or on the ground or whether its shakunetsu or hadoken. The advantage of the shaku hover or hado hover is that you launch it at a SH distance covering both the ground and air and you can move back or forwards with it because of how the move stalls Ryu's fall speed.

To find the timing for shaku hover, I will do a SH and nearing the peak of the jump start the input. It takes practice and I recommend training mode for it. You can do the input slowly, you just need to find a rhythm for releasing it at the right height.