I am currently gutting and renovating my future home which will be 5,100 sqft when everything is done. I have removed the old 5 and 3.5 ton HVAC and all duct work. My plan is to have a mini-split system installed and i hired a 3rd party company to run a Manual J, S and D for my house. I chose this individual because i believe that he had the expertise in mini-splits. I send him the CAD for the house and went over all the energy efficiency work i am having done like, spray foam on all exterior walls on the first floor and in the attic and triple pane high efficiency windows. When he came out we went over the the possible locations for duct work and he recommended LG’s mini split system. He came by the house and we discussed
 – placing two 18k low static units upstairs since we have easy attic access,
 – a  24k high static unit for the downstairs bedrooms
  – a 36k vertical system for a the downstairs common areas like kitchen, dining, living room etc.  
 – i had told him that i wanted to use rigid duct truck with flex ends wherever possible. He was hesitant because he thought flex would be fine. 

When i received the final plans, which are attached, he changed all air handlers to vertical handlers stating that the low static units cannot reach all the rooms. Based on what i have read the low static units are ideal for the upstairs and if i use rigid duct i should have no issue with air reaching these rooms. Any input would be appreciated.