I gotta do this!

Well, a few months ago, someone explained that the notch in the top of the Cox handles was for a throttle arm, but I just couldn't picture it.  Then I saw this eBay auction:  http://www.ebay.com/itm/251534086451?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Now I've gotta do this on a plane.  There's enough instructions in the pictures to figure everything out.  I have a case in my engine pile that has the hole drilled in it for the spring.  I also have a throttle sleeve ready to go.  I just have to make up a spring and the throttle arm for the handle.  Does anyone have one of these that can measure the length of the arm from the loop end to the handle pivot?  If not, I guess I can measure on screen the ratio of the handle width to the throttle arm length, and then measure the width of a handle I have on hand to get the rough length.

Here're the applicable pics if you don't want to look at the auction:




The Excited Mark