You might want to describe the configuration in a little more detail for a better solution to be provided. Type of roof .. shingle, metal, etc.? What is the frequency of the vertical antenna (what you're calling a ground plane antenna)? How far up the 13' mast is the OCFD (or windom?) connected. What are the two antennas fed with ... coax, open wire, single wire? All this will cause different interactions.
First of all THANK YOU for replying.
What I am planning on doing is actually setting up a inverted V off center dipole, the peak of the antenna would be approximately 13 feet above the peak of my roof which is 20 feet high, roof is a pitched roof with composition shingles an a wood frame structure. The short wire would extend about 45 feet to the chimney about 3 feet above the roof, the long wire would slop to the back fence about 12 feet above the ground with approximately 30 feet of the eighty foot actually on top of the fence at 8 foot above the ground. (Currently I have a center-feed dipole wire total length 120 feet stapled to the top of the fence at 8 feet with fair results) The antenna I was thinking of installing above the Inverted V is a Antron 99, 18 foot vertical with 4 - 72 inch counterpoises. The counterpoises slope down approximately 4 feet. I currently have a antenna tuner, antenna are fed with coax, vertical is 11 meters
I was also considering scrapping the vertical and raising the mast to 17 feet. My favorite frequency is 80 meters but would still like to be able to use 10 meters. Trying to get the biggest bang without upsetting the neighbors
Thanks for all the help