You can see how I got straight cuts on the overlap on my Yak-54 rebuild thread.
http://www.rcuniverse.com/forum/m_8377120/tm.htm
The covering portion starts at about Post #28 or 29. The 3/16: strips I cut out using a 4' metal straight edge and #11 blade. It worked perfect. I cut on one of those self sealing cutting mats from Tower Hobbies. I gave up trying to use the Top Flite strip cutter.
Ralph White, Neoga, IL