Topband: 160 top loaded vertical question

[cqtestk4xs at aol.com]

Planning on putting up a 160 vertical, but of course a 1/4 wave vertical is out of the question here in HI since we have a height limitation.

Here's the question:  I'm putting up around 50 feet of 3 inch aluminum tubing  (left over from various antenna takedowns).  I plan on putting up on top of that around another 10 or 15 feet of smaller diameter stinger for a total height of around 60-65 feet.  I obviously need to make up for the lack of height and I was planning on making a top hat of four wires coming down from the top of the antenna at around a 45 degree angle.  The problem is how long to make those wires.  My guess is around 25 feet based on my past experience in making Tee-topped 80 meter verticals.  However, it is only a guess and I don't feel like yanking the 3 inch pipe up and down a bunch of times to get it just right.  

I know some trimming will be necessary since this is not an exact science.  I just need an educated guess for where to start with the length.  Any ideas?

Bill K4XS/KH7XS