[Logikos]

In your postbit, or postbit_legacy find:

                <if condition="$post['signature']">
                <!-- sig -->
                        <div>
                                __________________<br />
                                $post[signature]
                        </div>
                <!-- / sig -->
                </if>

And replace with:

                <if condition="$post['signature']">
                <!-- sig -->
                        <div>
                                __________________<br />
<div style="width: 500px; height: 135px; overflow: hidden;">
                                $post[signature]
</div>
                        </div>
                <!-- / sig -->
                </if>

Then test it. Change the width and height to your convience.