Thought I was doing pretty good. Have been flying a Super Sportster solo for about a month. Had a bad landing last time out and had to replace landing gear and repair tail section. Also took out my Saito 72 (went into Funtana, I don't fly it!) and put in a brand new OS 70. Broke in the engine, had a rough couple of laps and made some adjusments to expo (was flying on 66% dual rates).
Well, I lost it!! Big crash, never to be found again. New engine, new landing gear and lots of time - gone. Those around me said I needed to gain altitude, problem was more throttle I gave it, the less control I had. Half throttle resulted in the nose dropping - and then the circle repeats itself.
It flew nothing like it did before the engine change, etc. Could it have been too nose heavy & powerful, making it next to impossible for an 'advanced' begiiner to deal with it??
I'm not sure when I'll be ready to do this again

Did you check the C-of-G? When major changes are made rechecking the balance is mandatory. I lost one of my birds last weekend (radio glitch) It happens!

Where did it go? Into some trees? Keep looking, those things can hide pretty good!

No, I didn't check CG, but I'm sure I will next time! Can it affect to the point that it's almost impossible for a relative beginner to fly? We tried to find it, but our field is surrounded by many little canals and heavy brush - can't even reach the area where I believe it went down. Hopefully, someone else may be more familiar with the land and knows a way to get around it.
Til then, I stick to my trusty old trainer.

Three words...

Yes, Yes and YES!

It can be to the point where the best flier in the world can't fly it.

As the saying goes, "Nose heavy planes may fly poorly, but tail heavy planes only fly once".