Personally, I've found that attempting to switch to Beast Form a split-second after you launch the fully-charged seed seems to make it considerably easier--for me, at least. Anyone else like to give it a try, see if I'm imagining things?
(My theory when I started was that Beast Form should always get the stratospheric jump, since if you're not in Plant Form the briars
always sting you and launch you a formidable distance when touched. I'm not at all sure if that's actually the case, or if it's something else--or if it's
anything but a two-bit superstition, for that matter.

)