I have to agree with C_Watkins
Sounds like it might be nose heavy
What your experianing is called a "High speed stall"
yanking on the elevator with those narrow wing tips can make the Cap stall/snap even if your CG is set perfectly

A nose heavy plane will tend to high speed stall where as a tail heavy plane will slow speed stall.

I typically like to set up my Aerobatic planes with an "Aft CG". This makes them more aerobatic and less prone to high speed stalling.
you just have to watch it when coming in for langing or flying very slow

Try setting the CG to the back off the range shown on the plans. once you get comfotable you can move the CG back more if you like

And ease into those loops don't yank the sticks so much, unless you trying to do a snap roll

Good luck