Width of extraspecial unipotent radical with respect to root elements

Let $G=G(\Phi,K)$ be a Chevalley group of type $Ф$ over a field $K$, where $\Phi$ is a simply-laced root system. We study the extraspecial unipotent radical of $G$ and prove that any its element is a product of not more than three root elements. Moreover, we prove that any element of the radical is, possibly after a conjugation by an element of the Levi subgroup, a product of six elementary root elements.