Changes i made:

Changed out engines, overhauled flight model, added flaps and (almost invisible) front landing gear. Plus i added some of my own tiny details. Also i changed the angle of the engines by a degree.

How to take off:
VTOL down for full flaps, then full throttle and pull up until you are off the runway. Once you are in the air, make sure you lift up the landing gear, as the landing gear make the aircraft dive downward.

TL;DR, fly it like a realistic airplane, not like a normal SP airplane

What i left for you to do:

Re-hide the wings (just scale them to 0)

Optionally hide the jet engines

Add infinite fuel tank (set masscale of a fuel tank to 0 then just crank up the fuel numbers)

Add a decorative rudder and something holding the back wing on. Some tape and two paper clips could work for the rudder (one straight up and the other angled)

Heres a version with most of the edits done

While i thought it would be more fun, i decided not to go this route as it doesnt fit the role of the aircraft. (Plus its a nightmare to get working. FT is finicky.)

all parts added from now on will need to be massless
and dragless in order to keep the current flight model