Yes, quite familiar with the principles. But it's not that simple.
Like
@Kayakguy, need for a safe foot plant puts an absolute upper limit on seat height. And at the limit of questionable safety (balls of feet barely on the ground), knee extension is inadequate for my long legs and dodgy knees. The larger V Rook frame was no help cuz all it does is extend reach, and reach is perfect as-is.
So, the only safe way left to get more knee extension was to move the seat away from the bottom bracket
horizontally. Luckily, the stock seat's long rails allowed enough setback to get my knees onboard with ebiking at low assist.
Big win in my book -- provided the one-bolt Selle Royal Essenza Plus seat is strong enough for the job.