Let us not forget that this is a person who is an "advanced" heli pilot and "can do anything" on the sim. I doubt that the advice against flying the 300S is going to have any effect. Generally speaking, the smaller the scale aerobatic airplane the more difficult it is to fly. The predictable end result is that the 300S in question is already dead and is simply waiting to crash.
I hope that chickenx5 is able to handle the airplane, fly it well and land it all in one piece. Unfortunately, I don't think that is going to be the case. If we don't hear from him again, it means the plane is history. However, I do wish him good luck.

Regards,
doubledee