Big models in JME3 cause too much lag when attached to the root node

This is the reason I used frustum because the model was clipping (right word?) when I got near it.
is there an other way to achieve this?
I used this method:
http://hub.jmonkeyengine.org/t/how-to-set-the-camera-near-clipping-distance/
However everything appears to be really thin.

EDIT: I suppose I should start a new topic for this…