These changes should make the Gnat_T1 useable on MPCarriers like the Nimitz.  
 As seen in the movie "Hot Shots". 
 
 At the end of Gnat_T1/Gnat_T1-yasim.xml, add:	
 
 <!-- Hook -->
	<hook x="-7.64"
				y="0.0"
				z="-0.24"
				length="0.80"
				down-angle="80"
				up-angle="-6">
		<control-input axis="/controls/gear/tailhook"
									 control="HEXTEND"/>
		<control-speed control="HEXTEND"
									 transition-time="5"/>
	</hook>
<!-- Launch-bar --> 
<launchbar x="1.85" y="0.0" z="-0.84" length="0.85">
  <control-input axis="/controls/gear/launchbar" control="LEXTEND"/>
  <control-speed control="LEXTEND" transition-time="1"/>
</launchbar>


in Gnat_T1/Hud/hud_Gnat.xml, add:

<!-- ====================================================== hook -->
<label><!--HOOK-->
	<x>-50</x> <y>50</y> <width>100</width> <height>6</height>
	<box>true</box> <halign>center</halign>
	<format>!! HOOK DOWN !!</format>
	<condition>
		<equals>
			<property>/controls/gear/tailhook</property><value>1</value>
		</equals>>
	</condition>
</label>
So that you have an indicator for HOOK DOWN


In Gnat_T1/Input/keyboard_Gnat.xml, add:

  <!-- map key for launch-bar -->
 <key n="76">
   <name>L</name>
   <desc>Launch-bar engage.</desc>
   <binding>
     <command>property-assign</command>
     <property>/controls/gear/launchbar</property>
     <value type="bool">true</value>
   </binding>
   <mod-up>
     <binding>
       <command>property-assign</command>
       <property>/controls/gear/launchbar</property>
       <value type="bool">false</value>
     </binding>
   </mod-up>
 </key>
<!-- toggle arrester hook -->
<key n="111"><name>o</name><desc>Hook toggle</desc>          
	<binding><command>nasal</command>
	<script>
		 if(getprop("/controls/gear/tailhook") == 0.0){
			   setprop("/controls/gear/tailhook", 1.0);
		 }
		 else{ setprop("/controls/gear/tailhook", 0.0);}
	</script>
	</binding>
</key> 


... that should do it!