Water spraying octocopter "set nav_use_midthr_for_althold =OFF" question

[hoglibogli]

hi there,

I have build an octocopter that carries water that it can spray.
So it has a changing weight and therefore changing hover throttle.
It varies roughly between 1500 and 1700.

I would like to use alt hold for this build and was wondering if "set nav_use_midthr_for_althold =OFF" would use the actual motor values that are used when engaging alt hold instead of using the "nav_mc_hover_thr".

So if I'm manually hovering with the throttle stick at around 1700 and "set nav_use_midthr_for_althold =OFF" and "nav_mc_hover_thr" set to 1500 f.e. would it jump or hold the altitude when engaging alt-hold?

Would it be better to set "nav_mc_hover_thr" to 1700 and have it jump up when hovering empty?

maybe someone can shed some light on this.

Thanks

Vincent