[Flatlandman]

If the plane is going to weigh 19 plus pounds and the wing area is 1800 plus then the da 85 will be fine. It weighs 4.2 pounds about the same as the evolution or mvvs 58 so i would use the da over the 58. That wing area will handle the total weight very easily. most 33%ers dont have that much wing area and fly at 22 pounds. The engine will have way more power than you will need so no full power level lines or down lines manage your throttle and possibly go 3 blade prop to absorb some of the excess power.

part 2 of your inquiry; giving it full throttle on up lines will give you full speed at that weight The throttle wont hurt the plane but the excess speed will so managing your throttle with respect to speed will be all you need to do