Air Conditioning - Specing AC for new home construction

I am building a new home and am ready to install central air. My house is a one level 2900sqft with a 550sqft office above the garage. The house is 2x6 contstruction with 1/2' plywood sheeting, wrapped in Tyvek and taped with Tyvek tap. The Tyvek was also pulled internally and wrapped and cut on the interior walls. I am Icyneneing the exterior walls (6"). then I am using R-13 for my interior walls and R-49 in my ceiling. I am also uisng R-19 for my floor as well as the entire gargage including my office above. The garagae will be sheetrocked with 5/8th. My windows and doors are Pella. The windows are listed at R-35 and my large slider which is the lowest rated is R-20.

My heat gain calc is about 36K BTU's. My plan is to use two 2 ton Carrier Infinity Series unots and split the house/office in half. I would then like to have 2 zones per unit.

What are your thoughts in using flex for the duct work? Or should I go with rectangular sheet metal. Also to carry the proper CFM's or LFM's what size of either or both should I use?

Thanks.

Id run the heat load again! 4 tons of cooling for a home in Boston with spray foam???? Id stay away from a zone system. they have to many problems. Why spray foam and Tyvek???? Id go with metal duct just because it will never have to be replaced like flex. Your home will be sealed well will you be using an HRV? Id go with 2 stage equipment to ring out more RH.

The Carrier Infinity series is a 2 stage approach.

Not sure about your questing of using Icynene to insulate my exterior walls of my house as well as rapping the house with Tyvek, thetaping the seams.

So are you thinking my he gain is mcuh less? Say 28K BTU's?

Carrier doesn't make half ton units. I also have a room above the main house that is 20x60 that I plan to finsih some day so an extra ton of AC would help.

The Carrier Infinity series is a 2 stage approach.

Not sure about your questing of using Icynene to insulate my exterior walls of my house as well as rapping the house with Tyvek, thetaping the seams.

Spray foam takes the place of a house wrap no need to do it because the foam will air seal.

So are you thinking my he gain is mcuh less? Say 28K BTU's?

Only way to know is to do a heat load on the home.

Carrier doesn't make half ton units. I also have a room above the main house that is 20x60 that I plan to finsih some day so an extra ton of AC would help.

Carrier does make units starting at 1.5, 2.5, etc.