.15 sounded small to me so I did a quick look for a general thrust of a .15 motor. I saw that a .15 is about 804g (1.77 lbs) thrust with an 8.4 prop. By those numbers I think that would be a struggle getting a 4.4lb plane off the ground. But this is not my expertise. Need actual thrust tests of your motors vs the wing loading and all that stuff that requires maths to understand.
I am sure others can point you at actual numbers you need to know for sure.