JRA , Having a 10: &2: grip is quite comfortable, hands on the front quarters.
down hill, i found having the brakelevers, at the rear , combined with putting your
weight back off the saddle descents are OK, but Magnus may have more
volcanic rutted unpaved routes he has ridden, than I.
Given his Location..
My 2 trekking bars share the installation of Rohlof's grip shifter. on them.
Avid speed dial levers, on 1 bike, Magura HS33 on the other..
[ITM-Koga-Miyata sourced, 3 types, 2 on bikes 1 not.]

options:
on Harris website they show setting them up like a Mustache bar ,
with Road type brake levers on the front. curve of the bars.
so there is that set up..

J bend Guidonnet levers like Velo Orange offers, may be something
to allow more side of the bar brake access ,
if set up to mirror the curve, under rear to side bend...