I'm installing a 2 ton goodman heat pump the house is 1000 sq feet,the duct work is flexible, 25 ft. long by 10 in. the R Value is 6. Is there anything wrong with the duct work I'm using.( to big, to small, wrong R Value, or does it matter.) North Carolina. Thanks

Do a manual J for equipment size. Then do a manual D for correct duct size and placement.

Are you doing the install yourself?
Are you a licensed, qualified technician?