If you have a high pitch prop, that could likely be your problem.
also, you could mix in some spoilerons if you want (upward deflection). This acts to kill the lift. It won't really slow the model much, but it will definitely force it to the ground. I wouldn't recommend it, though, unless you are fairly proficient at landing already. Add a little at at time as you see how the model reacts if you do it. Plus, flaperons are never a good idea because you are (in effect) going to force (or at least influence) the outboard part of the wing to stall first.

Edited to change a "brainfart"