How to move a prismatic (or other) joint to negative limits?

edit

When creating a prismatic joint between two links, it seems as though that initial distance between the links behaves as a "hard stop" for the joint.

If treating it like a spring, the initial position seems to be the "fully compressed" representation and all spring effects extend from that distance.

Is all this true? Does the "lower limit" = the initial distance between the links?

And if so, is there a way to work around this and move the joint lower than the lower limit (to bring the links closer together than their initial positions)?

(Note: This is an extension of this question.)

Example Code:                         
<model name='Pris_1'>
<link name='rod'>
  <pose frame=''>2.7415 -3.31431 1.27606 -1.5708 -0 -0.37111</pose>
  <inertial>
    <mass>1</mass>
    <inertia>
      <ixx>0.145833</ixx>
      <ixy>0</ixy>
      <ixz>0</ixz>
      <iyy>0.145833</iyy>
      <iyz>0</iyz>
      <izz>0.125</izz>
    </inertia>
    <pose frame=''>0 0 0 0 -0 0</pose>
  </inertial>
  <self_collide>0</self_collide>
  <kinematic>1</kinematic>
  <visual name='visual'>
    <pose frame=''>0 0 0 0 -0 0</pose>
    <geometry>
      <cylinder>
        <radius>0.003</radius>
        <length>0.1</length>
      </cylinder>
    </geometry>
    <cast_shadows>1</cast_shadows>
    <transparency>0</transparency>
  </visual>
  <collision name='collision'>
    <laser_retro>0</laser_retro>
    <max_contacts>10</max_contacts>
    <pose frame=''>0 0 0 0 -0 0</pose>
    <geometry>
      <cylinder>
        <radius>0.0025</radius>
        <length>0.1</length>
      </cylinder>
    </geometry>
    <surface>
      <friction>
        <ode>
          <mu>1</mu>
          <mu2>1</mu2>
          <fdir1>0 0 0</fdir1>
          <slip1>0</slip1>
          <slip2>0</slip2>
        </ode>
        <torsional>
          <coefficient>1</coefficient>
          <patch_radius>0</patch_radius>
          <surface_radius>0</surface_radius>
          <use_patch_radius>1</use_patch_radius>
          <ode>
            <slip>0</slip>
          </ode>
        </torsional>
      </friction>
      <bounce>
        <restitution_coefficient>0</restitution_coefficient>
        <threshold>1e+06</threshold>
      </bounce>
      <contact>
        <collide_without_contact>0</collide_without_contact>
        <collide_without_contact_bitmask>1</collide_without_contact_bitmask>
        <collide_bitmask>1</collide_bitmask>
        <ode>
          <soft_cfm>0</soft_cfm>
          <soft_erp>0.2</soft_erp>
          <kp>1e+13</kp>
          <kd>1</kd>
          <max_vel>0.01</max_vel>
          <min_depth>0</min_depth>
        </ode>
        <bullet>
          <split_impulse>1</split_impulse>
          <split_impulse_penetration_threshold>-0.01</split_impulse_penetration_threshold>
          <soft_cfm>0</soft_cfm>
          <soft_erp>0.2</soft_erp>
          <kp>1e+13</kp>
          <kd>1</kd>
        </bullet>
      </contact>
    </surface>
  </collision>
</link>
<model name='rope'>
  <pose frame=''>3.00263 -3.42589 1.02758 -3.0832 -0.749567 2.76636</pose>
  <link name='pivot'>
    <pose frame=''>0.4048 0 0 0 -0 0</pose>
    <inertial>
      <mass>0.1</mass>
      <inertia>
        <ixx>0.01</ixx>
        <ixy>0</ixy>
        <ixz>0</ixz>
        <iyy>0.01</iyy>
        <iyz>0</iyz>
        <izz>0.01</izz>
      </inertia>
    </inertial>
    <collision name='pivot_collision'>
      <geometry>
        <mesh>
          <scale>0.1 0.1 0.1</scale>
          <uri>model://ball.stl</uri>
        </mesh>
      </geometry>
      <surface>
        <contact>
          <ode>
            <min_depth>0.005</min_depth>
          </ode>
        </contact>
        <friction>
          <ode>
            <mu>1</mu>
            <mu2>1</mu2>
          </ode>
          <torsional>
            <ode/>
          </torsional>
        </friction>
        <bounce/>
      </surface>
      <max_contacts>10</max_contacts>
    </collision>
    <visual name='pivot_vis'>
      <geometry>
        <mesh>
          <scale>0.1 0.1 0.1</scale>
          <uri>model://ball.stl</uri>
        </mesh>
      </geometry>
    </visual>
    <self_collide>0</self_collide>
    <kinematic>0</kinematic>
  </link>
 </model>
 <model name='cylinder'>
  <link name='link_0'>
    <pose frame=''>5e-06 3e-06 0.5 1.5708 -0 0</pose>
    <inertial>
      <mass>1</mass>
      <inertia>
        <ixx>0.166667 ...