Many have echoed my experiences
with both a Hennessey and Clark. With the HH, having the foot end too low places my butt too close to the entry slit. Not uncomfortable, but not good for the stress on the slit. With the Clark, sliding to the foot end results in an uncomfortable lie.
I think Beep summed it up best with his description of gravity always winning.
And dang, when one tree is downhill from the other it is difficult to judge "level" and "slightly elevated". And I take pride in my transit-equipped brain!