I was just having a play in the SPH and found that I can't build this. I want to mount the tri-wing probe on the trolley, so when it reaches takeoff speed I can separate from the trolley and fly away... I've done similar before, but I used the "SelectRoot" mod, which doesn't seem to be available any more. I can't get it to work with the stock re-root function.
A couple of pics of the trolley and the aircraft:
It actually flies quite nicely for a thrown-together mess. Note the front fuel tank is empty for balance, not sure how it will fly as the fuel runs out...
Just for fun, I know there are much easier ways to launch a probe core.