Boost pressure control

For a boost control set up at high altitude what would be the best strategy for compensation and trim tables. We can decide how much boost we want to run at a certain altitude but the problem is when the client goes to a lower altitude road. Will it be better to set up boost target for sea level and adjust trims to get desired boost at higher altitud (were we are doing the tune) or set up trims at zero at the altitude we performed the tune and lower wastegate and boost compensation for lower altitude.

Also on another matter, sometimes when we finish doing the boost set up we perform a road test and we get different boost levels, specially at different gears even if we perform steady state tuning at 5000 rpm (not higher because of temperatures at the engine). How ca we proceed in a closed loop strategy to avoid this kind of boost behaviour?